What's up Ninja Nerds? In this video we're gonna be talking about fatty acid synthesis. This is part two. If you guys haven't already seen part one, go click on that, go check that out, really understand that because we're gonna go and dive into the really deep depths of fatty acid synthesis and again this is part two. Before we get started though please if you guys like this video and you guys really enjoy what we do please continue to support us by hitting that like button, commenting down in the comment section, and most importantly subscribe.
Alright Ninja Nerds, let's get into it. Iron engineers, when we talked about in part one of fatty acid synthesis, we went over basically all of this stuff. Let's just quickly recap it.
And then what I want us to do is at the end of part one, our goal was to be able to develop a couple substrates, three in particular, that we need to start building our fatty acid chain. Let's quickly recap what we covered in part one. We need to perform fatty acid synthesis. What do we really need?
Okay, we start off with glucose, right? Glucose. gets converted into pyruvate via the glycolytic pathway.
Then pyruvate will get taken up into the mitochondria in the presence of oxygen. So in this situation here, you would need oxygen present in order for pyruvate to get converted into acetyl-CoA to get taken up into the mitochondria. Once it's in the mitochondria, what happens with that acetyl-CoA? Well, you know acetyl-CoA will combine with oxaloacetate and make citrate.
And then citrate will have to go through the Krebs cycle. And eventually you'll make citrate. make NADHs, you'll make FADH2s, that'll go to the electron transport chain, you'll make ATP. The problem is when you're making fats, the issue is that you already have too much ATP.
There's already too much ATP that's being produced within these cells. So if there's too much ATP, because maybe you are already having a lot of glycolysis that's occurring, you're having a lot of fatty acid oxidation that's occurring, a lot of oxidative deamination that's occurring. Either way, there's lots of ATP. We don't need to make any more. So whenever there's lots of ATP, there's a very particular enzyme, right, that is designed to be able to convert citrate into isocitrate, okay?
But that enzyme is inhibited. And so citrate isn't able to be converted into isocitrate and go through the Krebs cycle because of high ATP. And so that will inhibit this continual cycling of the Krebs cycle. When that happens... citrate starts to build up.
Okay, so you start getting lots and lots of citrate. As that citrate builds up, what happens is there's a very specific protein present on the mitochondria that can spit citrate out of the mitochondria and into the cytoplasm. Once that protein allows for citrate to go out of the mitochondria and into the cytoplasm something very interesting happens. There's a very special enzyme called citrate lyase and what citrate lyase does is it basically undoes the reaction of when we went from acetyl CoA and OAA to citrate.
We're just going backwards. So citrate lyase cuts citrate and gives you oxaloacetate and acetyl CoA. But in order for us to us to be able to convert citrate into oxaloacetate in acetyl CoA this isn't citrate CoA so what we have to do citrate lice cut citrate into OAA and acetyl group so we have to add a CoA on now let's go up this pathway for a second what happens with that OAA the OAA the oxaloacetate will get converted into malate now here's what I want you guys to remember which is important malate will eventually get converted back into pyruvate and basically all you're doing here is you're going from a three this is actually going to be what a four carbon structure and then you're going to a two carbon structure when you go from malate to pyruvate there's an enzyme that catalyzes this step and this is called a malic enzyme what I want you to remember is that the malic enzyme is important for converting malate to pyruvate but also within that step of going from malate to pyruvate you generate some very important molecules that we're going to need as pre-curve to fatty acid synthesis, and this is NADPH.
I want you to remember NADPH as one of the three things that we need to start building the fatty acid chain. I want you to remember that this is the guy with what's called the reducing power. It's going to be a very strong molecule that we use to reduce particular molecules in the fatty acid synthesis pathway.
Okay? So that's one way that we get NADPH is from converting malate to pyruvate via the malic enzyme. Another way that we get NADPH, you guys know another way?
You know there's a very specific pathway called the pentose phosphate pathway. The pentose phosphate pathway, a very, very brief discussion here, is we take glucose, right? And we convert into what's called glucose 6-phosphate via the hexokinase enzyme or glucokinase in the enzyme depending upon what tissue we're in Then glucose 6-phosphate You know what happens is it can eventually go down the glycolytic pathway or it can go into what's called the pentose phosphate where eventually It gets converted into what's called ribose 5-phosphate and then during that process of where you make ribose 5-phosphate You can generate NADPHs.
So from the pentose phosphate pathway we can generate lots of NADPHs as well as we can generate NADPHs from the malic enzyme converting malate into pyruvate. Now we have that one precursor. We got two more that we have to talk about.
The other precursors we have to go down this pathway. So we take citrate, we had the citrate lice cut it to give us OAA, to give us malate, to give us eventually pyruvate to give us an NADPH. The other component is we go to acetyl-CoA. Now what happens with the acetyl-CoA?
The acetyl-CoA is a what? It's a two carbon structure. What I wanna do is I wanna add on another carbon to it. So I'm gonna do what's called a carboxylation reaction where I add a CO2 onto acetyl-CoA to make malonyl-CoA.
which is a three carbon structure. So this carboxylation reaction requires an enzyme, which is called acetyl-CoA carboxylase. And we talked about this in great detail in the part one. This is an important enzyme. The reason why is that this enzyme requires lots of things.
It is basically the rate limiting step within fatty acid synthesis, highly regulated step. Lots of things can alter or modify the activity of this enzyme, which determines the activity of the enzyme. determines this type of reaction, going from acetyl-CoA to malonyl-CoA. Why is this so important? Malonyl-CoA is one of the other substrates.
This is going to be the building block, if you will. I like to remember this guy as the building. Block for fatty acid synthesis. I need him in order to keep building my fatty acid chain.
So very very important to remember malonyl-CoA. Really quick recap of the acetyl-CoA carboxylase. This enzyme catalyzes this step but there's enzymes and different types of molecules that either allosterically regulated or regulated by phosphorylation reactions if you guys remember insulin can help to stimulate this enzyme okay so it has the ability to stimulate this enzyme by pulling phosphates off. Citrate can allosterically regulate the acetyl-CoA carboxylase enzyme. It can bind onto a particular portion of it, change its structure, making it more active.
Particular hormones like glucagon, norepinephrine, epinephrine, they have the ability to regulate protein kinases, which will phosphorylate the acetyl-CoA carboxylase, inhibiting this enzyme. And then long-chain fatty acids. Think about this one.
What's the goal of making these molecules? To make fatty acids. If you already have... have lots of long chain fatty acids would you want to make more no so it's kind of gonna act as a regulator being able to say hey too many fatty acids don't stimulate this enzyme because I don't need any more of this because I don't want to make more fatty acids so again that's the process and the other way I like to think about insulin and then glucagon as the opposer is insulin loves to build things up so wants to make fat make protein make glycogen glucagon norepinephrine epinephrine these are stress situations they want to break things down. They want to break down glycogen.
They want to break down lipids. Okay? So very important to remember that. All right, so we have the two things we have. NADPH, one from the pentose phosphate pathway and from the malic enzyme pathway.
We have malonyl-CoA, which we got from acetyl-CoA being carboxylated by this important enzyme called acetyl-CoA carboxylase, which is a rate-limiting step in fatty acid synthesis. Highly regulated. What's the next thing that I want you to remember?
Before we go on to the third substrate, there's a... There's another thing that you need to remember about malonyl-CoA. It's really good, not only at being able to be a very important building block for fatty acid synthesis, but it also can regulate the activity of very particular types of proteins which are present on the mitochondria.
You know in the mitochondria you have different types of proteins here that we have them kind of listed here in pink. It's kind of beautiful in that sense. Look, you see this?
It's in the shape of a one. This is actually called CPT1. Sometimes we also call it CAT1. one, carnitine palmitoyltransferase type 1 or carnitine acl-transferase type 1. And this one is carnitine palmitoyltransferase type 2 or carnitine acl-transferase type 2. Either way, malonyl-CoA inhibits this enzyme, okay?
The carnitine palmitoyltransferase type 1. In general, why is this important? You're probably like, what the heck does this have to do with anything? You know these proteins, they're important for basically allowing for the translocation of bacteria.
fatty acids into the mitochondria. Because once these fatty acids get into the mitochondria, they go through a process called the mitochondrial process called beta oxidation. and beta oxidation basically is gonna be used to make ATP.
Well, we already have too much ATP. So if we have so much ATP, do I want more fatty acids coming in here getting oxidized? No, I'm trying to build fats up. So when you have lots of malonyl-CoA, it inhibits these carnitine-pulmitol transferases so that no more fatty acids get taken up to get broken down so that we can build them. Isn't that cool?
I think it's pretty cool. All right, the last substrator kind of thing that we need here, we have NADPH, malonyl- the third one is a very particular enzyme. What is this enzyme? Let's take a look here.
This enzyme here in purple is called the fatty acid synthase type 1. What is this purple enzyme here called? This is called fatty acid synthase type 1. We're going to call it FAS1. This is a very special enzyme. Now this enzyme FAS1 has two particular components on it that you actually do have to know and we're going to go into most detail of it throughout the video.
one end of it it has a cysteine residue with a thiol group okay and on the other end it has this ACP structure what the heck is this ACP is basically the acl carrier protein and what happens is there's a structure here called a phospho a for fossil pentothion that makes up this ACP kind of group with the sulfhydryl group but all I want you to know is that there's two components of the fatty acid synthase and this is the enzyme that we're going to be utilizing to make fatty acids there's two components of it one is the cysteine component with the sulfhydra or the thiol group and then the second one is the ACP group which is the acyl carrier protein which has the sulfhydra group these are the very very important components here so we have three components for fatty acid synthesis NADPH which is the reducing power malonyl CoA which is our building block which to make fatty acids and then fatty acid synthase type 1 is our enzyme or the catalyst if you will that's going to help to propagate this entire process so now that we've built our building blocks we have the things that we need let's actually go through the process of how build fatty acids. Alright, so we have to go through step by step and build up this fatty acid chain. So we have our three precursors, we're going to use them sporadically throughout these different steps.
Okay, so again, remember what were those three things? NADPH, malonyl-CoA, and then the last one is the fatty acid synthase type 1. There is another player that kind of like pops in every now and then, and it's acetyl-CoA. And again, he's an additional one that will be floating around that we can have in there. So if you really want to, you can have three plus an additional one acetyl-CoA.
So a malonyl-CoA. an acetyl CoA, an NADPH, and then the fatty acid synthase type 1. All right, let's go through step one here. Step one is we have to add an acetyl CoA group onto the ACP end.
That's the first thing that has to be done. So we're going to add an acetyl group. An acetyl group is how many carbons? Two carbons. I want you to remember that.
So what I'm going to do is I'm just going to draw circles, which is going to represent my carbons here. And then again, this is acetyl CoA, so it's going to have that coenzyme A popping off here, right? So what I'm going to do is I'm going to add this into the first step and I'm going to add it onto the ACP end, right? The second thing is when I add this acetyl-CoA group on, I can't have the CoA because I need that end to add it onto the ACP. So I'm going to pop that CoA off in this step.
Now the enzyme that is utilized in this process here is a very special enzyme. And this enzyme is called... Acetyltransacylase.
So again, all this enzyme is doing is, it's transferring the acetyl group, the two carbon group of acetyl CoA, onto the ACP end. So what would it look like over here then? If we were to have the result of this step, we would have, again, a two carbon. kind of molecule hanging off of that ACP end.
Particularly, if you really want to be particular, it's going to be binding to that sulfur group there on the actual sulfhydro group. Okay? So that's the first step here. The second thing that we're going to do, okay, so first thing, we added an acetyl-CoA group onto the ACP end using an enzyme called acetyltransacylase. The second thing that we're going to do is we're going to have, let's pick up where we left off here, where we had the two-carbon structure here, the acetyl group hanging off the ACP end.
Now what I want to do is I need room for the malonyl-CoA to bind onto that ACP end. So I can't have these two-carbon groups sitting here. So what I'm going to do is I'm going to transfer these two-carbon groups onto the system.
residue I'm going to transfer it from the ACPN Onto the cysteine end. So an enzyme is utilized to transfer that and we call this enzyme acyl, not acetyl, acyl trans acylase. Okay, and what is going to happen in this step is I'm just going to transfer these two carbons onto the cysteine group. So what that look like over here?
So now what I would do is is I would have the two carbon groups hanging off of the cysteine group, the acetyl group there, and if we were to just be particular here The ACP group is now going to be back to that sulfhydryl component like that. Okay? So that's that step.
And here, we can just kind of put here, to make it easy, we can put a transfer of these two little acetyl groups there. Okay, that two-carbon acetyl group. All right, that's the second step.
So first one, add an acetyl group onto the ACP end. Second step, transfer it from the ACP end onto the cysteine end. It's kind of like, why didn't I just add it to the cysteine end the first place? Who knows why these things happen?
All right, the next thing, the third step here, let's pick up, we have the two carbons here on that cysteine end. Now I have space here on that sulfhydryl group, okay, to be able to add on my malonyl CoA. So what can I now add? What I'm going to do now is I'm going to add on a 3-carbon structure.
Because you know malonyl-CoA is a 3-carbon structure. We've already discussed that. So we're going to add a 3-carbon structure into the form of malonyl-CoA.
We can't have the CoA because we need that end to bind to the actual ACP group. So we pop off that CoA. In order to do that, I need a very special enzyme to catalyze this step. And this enzyme is called malonyltransacylase. And all we're going to do is we're going to add the malignant group onto the ACP end.
So let's look at what this would look like afterwards. We still have that two carbon acetyl group on the cysteine residue bound particularly to the thiol group. And then the ACP component.
here is going to have that malonyl that three carbon structure which is going to be bound to it okay beautiful so that is the third step first step added the acetyl CoA group transfer to the ACP and second step transferred it from the ACP to the cysteine. Third step, added the malonyl group onto the ACP end. All right, so we've covered the third step. Let's talk about the fourth step.
So let's pick up where we left off, okay? So what do we have here on that cysteine end, okay? That cysteine group, technically bound to the sulfur of that thiol group, is our acetyl group, right? Then on the ACP end, we should have that malonyl group, that three-carbon structure.
Okay, here's the next goal. What does that mean? With the first round of fatty acid synthesis, the goal is to make four carbons, like a four carbon acyl kind of chain, as like the precursor, and then for the remaining steps, it'll be two carbons at a time.
But the first one, we need four carbons. So how many do I have so far? I have three with malonyl, and then two from the acetyl CoA group. Okay, so that's a total of five.
That's too many. So when I combine these together, I'll get five, so I'm gonna have to pluck one off. When I pluck one of those acetyl groups off, what is that called when you pluck off one of these in the form of CO2.
It's called decarboxylation. So what we're gonna actually do here is what's called decarboxylation and that's basically popping off a carbon in the form of CO2. Now there's a very special enzyme that will take these two carbons from the cysteine group, add it on to the ACP end, condense them, and then before it condenses it pops off a carbon.
carbon in the form of co2 what is the name of this enzyme this enzyme is called acl malonyl ACP condensing Enzyme. It's like holy crap that's one heck of a name but this is the enzyme that's going to drive this step. So what will happen is that you will do what?
You're gonna kind of transfer these over here so at the end of this you're gonna transfer two over but pluck one of them off and then smash them together on the ACP end. So at the end of it what will it look like? Well the cysteine residue isn't going to have any more carbons bound to it so it will have that thiol group there.
The ACP end however is now going to have what? It's going to have three carbons. We're going to represent these in red because that was the malonyl. And then it's only going to have one of the carbons from the acetyl group that was on the cysteine in because the other one got plucked off. That's a total of four carbons now that we've built up at this point.
Okay? That is going to be the beginning of our fatty acid chain. So now that we've done that, we've gone through the first four steps, let's go through a couple more where we take now this four carbon structure, which is in a very specific form, and we'll talk about it.
It's what's in the form of a beta ketone. Okay, so we'll talk about that in just a second. But what we're going to need to do from this point on is modify the activity of that beta ketone for the remaining next steps.
So let's go there. All right, so let's continue, guys. So we left off where?
What do we have kind of sitting on that cysteine residue? Nothing at this point, right? We transferred everything from that onto the ACP end.
So on that cysteine residue should just be that thiol group. That's where we left off. And then on the ACP end, we should have the condensed version of the three carbons of the malonyl. And then that one carbon of the acetyl group, because we plucked one of them off via the decarboxylation, right?
And then one of the... important things that we said here is if we actually look at this entire structure and really zoom in on it at the actual like organic kind of chemistry level we'll see here that we have that ACP group which is bound carbon double bond oxygen there and then again you have another carbon here, you'll have another carbon there, and then you'll have this kind of structure. And then we call this the beta ketone, right? What part of this was the beta ketone? It was actually this part that was the beta ketone.
Our goal for this next step here is to take this beta ketone and actually spread some electrons in the form of hydride ions across it. The ultimate goal is to turn this into a hydroxyl group. So remember I told you that there was a couple players that were involved.
We said Acetyl CoA kind of gets mixed in and then we said that Malonyl CoA gets mixed in and then the Fas, the fatty acid synthase is involved. What was the other one? NADPHs.
They're coming in baby. So NADPHs are really cool here. They come in, they drop some of the electrons off in the form of hydride ions and the ultimate goal here is you're gonna get the same product throughout a lot of these steps here.
You're gonna have this thiol group here. and then on that ACP end here you're going to have the three carbons. The number of carbons isn't going to change, it's just the different structure within that four carbon component here that's going to change a little bit.
So if we were to really zoom in, what happens now after we do this reaction? We're going to take that ACP group, we're going to have that carbonyl group there, carbon, and now where the beta ketone was, I have a hydroxyl group. What is this called?
This is called a hydroxyl group. That was the goal of this fifth step here. Now there's a special enzyme that's involved in this step, which is taking the beta ketone of this acyl group and converting into a hydroxyl group.
The enzyme is called, it actually kind of works out nicely, it's called beta-keto-acyl-acp-reductase. It's actually perfect how this is named. You want to know why?
The beta-keto-acyl-acp-reductase. ketone of the acyl group on the ACP end is getting reduced by who? NADPH. That's kind of a nice beautiful thing there. So that's the fifth step.
The sixth step, let's continue on here. Again, throughout all of these, you're going to have that thiol group. So here, we'll just, for right now, this is not going to change throughout these steps for a while. So here, let's just get these out of the way. These aren't going to change for a bit.
On the ACP end, again, the number of carbons isn't change for a while as well. So we're still gonna have three carbons here, we're still gonna have three carbons here from the malonyl, and we're still gonna have that one carbon from the acetyl group in these next steps. The only thing that's really going to change is the different components of that four-carbon group. So what do we leave off here?
We have that ACP group. Carbonyl, carbon, and now we have a hydroxyl group here. What do I want to do now?
The next goal is to take this hydroxyl group, get rid of it, and yank out something in the form of water. So I actually want to dehydrate this molecule. So I'm gonna yank water out of it. When you yank water out of this molecule, what is it gonna look like at the end?
Imagine me pulling water out of this. What happens is you get something like this. The ACP, you get that carbonyl group, and then again you're gonna get kind of a double bond here.
You'll get hydrogens that'll span across this, and then a CH3. Okay, so it's still four carbons, but now there's no longer a hydroxyl group, there's a double bond. Okay, the enzyme that performs this step is very cool.
Okay, now here before we actually tell you the name of it, you know when we number things according to organic chemistry, we start with the highest functional group. group highest priority so are you pack style this would be the number one, two, three, four. The third carbon is the one with the hydroxy group. So we actually use an enzyme called 3-hydroxy-acyl-dehydratase.
Think about this, on the third carbon of this acl group there's a hydroxyl group we're going to dehydrate it by pulling water out. It's a perfect kind of thing there. Okay, go on to the next step. At this next point here we're still gonna have the same component here we still have that hasn't changed we still have the four carbons three of them are from the malonyl group one of them is from the acetyl group okay that doesn't change it's also gonna be the same over here they're still gonna be a total number of what you're gonna have four car carbons here, three of them are from the malonyl group, one of them is from the acetyl group.
Okay, beautiful. So what's changing? It's just the different components. Let's leave off here.
What do we have here? We have that ACP group, we have the carbon double bonded to oxygen, we have a carbon, we have a double bond carbon, and then we have that methyl group, and then we have H's right there. Okay? So this is a double bond. Okay?
We call this over here, we call it a hydroxyl group. This thing here, this kind of like structure here. is actually called a enoyl. What is it called?
It's called an enoyl. What I want to do is, is I want to take this double bond that's in the form of what's called an enoyl, and I want to spread hydrogens across this entire thing. I want to get rid of the double bond.
So in order for me to do that, I have to add more hydrogens across that double bond. Who did we use before to add hydrogens to things? The NADPH. It's back, baby.
So NADPH. ADPH comes back and adds on some hydrides. Okay, so we're gonna reduce this actual molecule here.
So what is it gonna look like afterwards? Well, imagine we added hydrogens across that double bond. So carbon, double bond oxygen, carbon, and now there's no double bond there, so it should just be a carbon here, right?
We added hydrogens across this. So this should be a CH2 and a CH2 there, because I added a hydrogen to this one and I added a hydrogen to this one. So now there's no double bond. bond. It's just a nice like saturated fatty acid.
There's no double bonds present. This is our nice acyl group, okay, for our fatty acid chain. That is what we want at the end of this kind of process. Now, this thing is called an enoyl.
We're reducing this. So guess what the name of the enzyme that catalyzes this. It's called an enoyl.
The enoyl on the ACP end is getting reduced, reducted. and then this is the end structure here okay okay now that we have that let's pick up here at this last part here this is kind of our four carbon structure here that we've really formed out this is we're pretty much at the end guys of this process but let's say for a second okay we've really started off or we've really got our fatty acid kind of chain beginning we have four carbons that we're gonna start with let's say that we continue we're gonna continue to do this process until we can kind of have an idea here of what it's going to look like. How do we keep adding things on?
So let's say that we start back from a previous couple steps here. Remember there was another enzyme that transferred the ACP molecule, transferred the molecules from the ACP group onto the cysteine group. Do you remember what that enzyme was called? It was called acyl trans acylase and all it did is it's just going to transfer this group of four carbons onto that cysteine group so what should this look like afterwards this should look like this now i'm going to have the three carbons here from the malonyl group and then i'm going to have that that carbon from the acetyl group there okay all of it's going to be in this format though that opens up the acp end right so now the acp end is open because it has that So if hydro group here that you can add something on, what can I add on here? I could add on another malonyl-CoA and then start this process all over again.
So let's kind of just get a quick idea and to test your knowledge and see if you guys remember all those steps really, really quickly. So go to the next thing and see if we can review quick. All right, so let's test you guys'knowledge. All right, let's see if you guys remember these things, engineers. So we had the acl-transacylase, right?
And it basically transferred things from the ACP end onto the cysteine end. Kind of that fatty acid chain that we've already kind of been forming here at this point. Three of them were from the malonyl group, right? And then that one was from the acetyl group.
And so far, it's all in that saturated fatty acid form. On the ACPN, though, it's free. It now has that sulfhydryl group that is ready to bind on to something.
So now what we're going to do is, is we're going to use that enzyme, what was the enzyme before, that we utilized to add in a malonyl CoA, and in the process we spit the CoA off. That was called malonyltransacylase, right? So that was called malonyltransacylase. aclase enzyme so that enzyme is going to stimulate that step to add the malonyl group onto the ACP end so what should this look like at the end of this now so you're still going to have that three carbon thing there from the malonyl group but now you're going to have the three carbon here from this new malignant group on the ACP end and then we still have that one carbon from the acetyl group there.
Okay, this is what it should look like and then what was the next step after that we want to do what? We said the The first thing you should have four carbons as the beginning building block for fatty acid synthesis. From that point on, how many do we want to add? We want to add in two carbons kind of at a time. So now what I'm going to do here is, is I'm actually going to add this whole kind of group here on.
And in the process I'm going to have to pluck one of those carbons out. So I'm going to condense it down and pluck a carbon out. So that's what we're going to do here in this kind of following step here.
All right. right so if we continue here right so let's let's say here again we have the three carbons from the new malonyl group we have the three carbons from the old malonyl group from the first cycle and then that one carbon of the acetyl group right what's the goal here the goal is to go back to what we had when we had that condensing enzyme you know the condensing enzyme that we have before it's basically going to combine this carbons here onto this one and then what did it do it plucked out one of the carbons and the form of a decarbonized reaction, right? So it popped off one of those carbons here. Let's just say that we pick any of them, we're just going to say that we pop that blue one off there, since it's just so random.
Okay, so we're going to pop that off in the form of a CO2, that's called a decarboxylation reaction. Okay, now what would that look like after I fuse these three red carbons with these three red carbons here? It would look like six red carbons, right?
So I'm gonna have one, two, three, three, four, five, six here. And then I transferred them all from the cysteine group. So is there anything on the cysteine group?
No, so it's gonna have that thiol group there on the end. Remember what I told you, the first round of fatty acid synthesis, there's gonna be four carbons as the building blocks. From that point on, from every remaining cycle until you build a 16 carbon fatty acid, you add two at a time on.
Okay, so these were the OGs. These are the These were the original four. And then these are the additional two carbons that we're going to keep adding on one after another after another after another.
So here's what I want you guys to remember because this may come up on the exam. If there was a 16-carbon fatty acid that you had to make, the first round was four carbons. So that's a total of 12 carbons.
How many rounds would you have to go after that first cycle? How many times would you have to do what we're doing now until you make a total of... 16 carbon fatty acid. Well, two carbons at a time, so 12 divided by two is going to be six rounds.
So I have to do six additional rounds from the first time that I started. So it's a total of seven rounds for fatty acid synthesis to occur. All right.
What was the name of this enzyme? Just to test your knowledge. When we condensed it down, we condensed the malonyl group with the acyl group. It's called the acyl malonyl ACP condensing enzyme. All right, beautiful, and that was catalyzing this step.
Now, from that point on, what do you guys remember? Well, here, we're going to have our six carbons here, right? And then we're going to keep building on. So one, two, three, four, five, six. If you guys remember, let's see if you guys remember here.
This is going to be in the form of a beta ketone. We go from the beta ketone, right? We take the beta-keto-acela-ACP reductase, and eventually we're going to... convert this into a hydroxyl group. Then we're going to take another enzyme called the 3-hydroxyl ACP dehydratase and pull water out of this.
And that is going to give you a double bond here, right? That's going to give you your enol group. And then the last step is that we were going to do what after that? And after that we're going to take and splash hydrides across that double bond and then eventually convert this into a Kind of a growing fatty acid chain in that sense. We're going to saturate that.
So at the end of this, it's still going to be, after we went over all these remaining steps that we've already talked about before, it's still going to look like this. But let's imagine that we continue this step over and over and over and over and over again. What's going to be like at the end of this? You're just going to continue to keep building on.
One, two, three, four, five, six. This is going to look the same after you do all of these steps that we talked about before, right? Going from the beta ketone to the 3-hydroxyacyl group to the enoyl and to the saturated fatty acid.
And then what will you do there? You'll transfer that onto the cysteine group and then you'll start the whole process all over again, right? But let's say that we just continue to keep doing that. So let's come down here for a second. Let's say that we continue.
We do a whole six rounds from that point on. And eventually we have at the end of this. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16. I have my 16 carbon fatty acid which is bound to this ACP group. I want to liberate this fatty acid away from this fatty acid synthase.
How do I do that? There's a special enzyme called a thioesterase. which is going to be utilized to cleave this completely grown 16 carbon fatty acids.
This is 16 carbon fatty acid in the form of what's called palmitate or palmitic acid, one of the two. We cleave that from the ACP end, and that is how I grow my fatty acid chain. Okay?
Ninja Nerds, I hope that made sense. All right, Ninja Nerds. In this video today, we talk about fatty acid synthesis, and this is part two. I hope it made sense.
I hope that you guys did enjoy it. As always, Ninja Nerds, until next time.