Amino Acid Metabolism Lecture Notes

Introduction

• Discusses amino acid metabolism
• Focus on energy utilization from amino acids
• Transamination process in muscles and liver involvement

Amino Acids in Muscles

• Amino acids necessary for protein synthesis
• Example amino acid discussed: Alanine
  • Structure: NH3⁺ group, alpha hydrogen, methyl group, carboxyl group
  • Zwitterion form: neutral overall charge

Transamination Process

• Alanine reacts with Alpha-ketoglutarate
• Enzyme involved: Alanine Aminotransferase (Transaminase)
  • Facilitates swapping of groups between molecules
  • Uses cofactor: Pyridoxal Phosphate (derived from Vitamin B6)
  • Reaction involves a Schiff base linkage

Reaction Outcome

• Alanine becomes Pyruvate
• Alpha-ketoglutarate becomes Glutamate
• Pyruvate can convert to:
  • Lactic acid (Cori cycle)
  • Acetyl CoA (enters Kreb Cycle for ATP production)

Pyruvate Metabolism

• Pyruvate has two main pathways:
  • Lactic Acid Production
    • Cori cycle: Converts lactic acid back to glucose in the liver
  • Acetyl CoA Formation
    • Enters Kreb Cycle, leading to ATP production

Glutamate and Ammonia

• Glutamate transported to liver
• Undergoes Oxidative Deamination via Glutamate Dehydrogenase
  • Produces Alpha-ketoglutarate and toxic Ammonia
  • Ammonia converted to Ammonium and enters Urea Cycle

Additional Amino Acids

• Aspartate example:
  • Reacts with Alpha-ketoglutarate
  • Enzyme: Aspartate Aminotransferase (Transaminase)
  • Produces Oxaloacetate and Glutamate
  • Oxaloacetate enters Kreb Cycle

Amino Acid Metabolism Significance

• Amino acids contribute to ATP production
• Amino acids can also be converted to glucose (Gluconeogenesis)
• Enzymes involved are reversible, aiding flexibility in metabolism

Clinical Relevance

• Elevated enzyme levels (AST, ALT) in blood tests indicate possible liver or heart damage

Conclusion

• Amino acids are versatile energy sources
• Transamination and deamination are key processes
• Next topic: Urea Cycle