with enzymes there are various things you can do in order to regulate the function of them and what we'll be talking about is three different approaches for that which you may see described as ace ace allosteric regulation covalent regulation and regulation of the enzyme itself now looking at this list you may notice that something known as competitive inhibition is absent and the reason for that is that competitive inhibitors the way that they operate is that they're something that isn't the substrate but they occupy the active site and so essentially it distracts the enzyme from being able to function on the substrate but notice the competitive inhibition does nothing to the function of the enzyme itself it simply makes it harder for the substrate to bind the enzyme and so all three of these are different ways that you can regulate the function of the enzyme by up regulating it or down regulating it so first we'll start with allosteric regulation allosteric regulation which remember in contrast to competitive inhibition you have non-competitive inhibition you might see allosteric regulation listed as a type of non-competitive inhibition and the reason is that the regulator in allosteric regulation is not in the active site but instead at some other site on the enzyme and when it is in that other site it often will induce a change in the conformation of the enzyme or something else that makes that enzyme oftentimes it will inhibit it will make it less likely to be able to operate with and catalyze the reaction that you're trying to catalyze and so allosteric regulation the key thing to realize is that the binding site is not at the active site so if we have an enzyme here like this and we'll just say this is the active site the allosteric regulator might bind somewhere down here and in doing that it might induce a change in the shape of the enzyme and as a result it might for example inhibit or completely inactivate the enzyme from being able to function as a catalyst so allosteric regulation is when you have something binding at the non-active site but somehow that changes the conformation of the enzyme such that it no longer functions at the exact same level that it previously did when the allosteric regulator was absent so the key thing there non-active site that's what you should be thinking when you look at allosteric regulation the next one is covalent regulation and it's important to note that this is reversible covalent regulation and you see this a lot with phosphate groups although other groups like methyl groups and acyl groups and other ones like that can also be used to regulate enzyme function a lot of enzymes if they're phosphorylated they might become active or they might become inactivated phosphorylation doesn't necessarily mean activation of that enzyme sometimes phosphorylation means that the enzyme is actually going to either be inhibited so it will reduce its function or completely inactivate that enzyme but the key with this is that it's reversible covalent modification and usually that involves a phosphate group although other groups like methyl groups are possible the third one is with the enzyme itself and what this usually refers to is zymogens z-y-m-o-g-e-n and zymogens will often have the ending o g-e and o-gen and so one example that you're very very likely to encounter is pepsinogen pepsinogen is secreted into the stomach and then when it's in the stomach if it encounters the hcl that makes this environment very acidic that will cause the zymogen the pepsinogen to be cleaved and as soon as it gets cleaved it then it turns into its active form of pepsin and so a zymogen which may also be known as a pro-enzyme is something that is irreversibly activated when the ad the molecule is cleaved so it's activated by cleavage and you might see that uh the most common one that you'll see is pepsinogen although there are many many other zymogens you encounter and so many of them like trypsinogen and other things like that will have the ogen ending and so zymogen or a pro enzyme is something that is released in its inactive form and then when you cleave that pro-enzyme or zymogen it then becomes irreversibly activated and thus it becomes useful for catalysis and it can help facilitate different reactions so as far as regulation of enzyme function goes these are the three ones that you'll see come up again and again allosteric regulation which is either activation or inhibition or even inactivation by something binding to a site other than the active site of that enzyme covalent enzyme regulation is usually involving phosphate groups and when the phosphate group is attached to that enzyme then it either becomes activated or inactivated and then the enzyme itself can be involved in regulation if it's secreted as a zymogen a large inactive form then it can be cleaved by some conditions for example the acid in the stomach into its active form and then function by performing its enzymatic catalysis so these are the big three for regulation of enzyme function allosteric regulation at the non-active site covalent regulation usually involving a phosphate group and then the release of xymogens which are irreversibly activated once you cleave some of the bonds sometimes the allosteric regulator will itself be a downstream product of that enzyme so essentially by the enzyme producing that product that product can now come back and say there's enough of us that you no longer need to function at the same level and thus they can down regulate the function of that enzyme so be aware of downstream products being allosteric regulators in a lot of negative feedback loops