protein metabolism

• nonessential amino acids can be synthesized using carbon skeletons of glucose and citric acid cycle intermediates
• Transamination: reversable reaction in which an amino acid is converted to a different amino acid
• Aminotransferase (PLP): vitamin B6, acts to conduct transamination
• Glutamate and Nitrogen: adding N group to glutamate to make glutamine
• Aspartate and Glutamine: adding N group to aspartate to form aspargine and glutamate
• transamination: removing N from AA and transferring to another C skeleton, proteolysis and AA catabolism, up during fasted states
• Proteolysis: aminotransferases have preferred AA/keto acid substrate and use aKG/glutamate as the counter keto acid/AA
• Valine, isoleucine, leucine: transaminated into glutamate which then can become alanine so that it can move through the blood
• Branched chain AA + aKG = keto acid + glutamate
• Muscle proteolysis: want to release alanine to liver to then make glucose, if releasing pyruvate then ammonia will stay in muscle
• From glutamate: amino groups released as ammonia to then be made to urea, ammonium, or synthesize other AA. The C skeleton in this rxn can go to TCA cycle to make into citrate and stored as FA (if excess AA)
• Glutamate + NAD + water (uses GLUD) = aKG +NH3+NADH + H: this is deamination
• Deamination: amino groups can be released as ammonia from glutamine
• Glutamine + water (glutaminase (GLS)) = glutamate + NH3: NH3 goes to liver to make urea or kidney as ammonium
• Deamination: amino groups can be released as ammonia from asparagine, asparagine + water (asparaginase) = aspartate + NH3