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Nitrogen Cycle. Summary of Protein and Amino Acid Metabolism. (transaminase). Transamination. Common acceptors: -ketoglutarate (glutamate) pyruvate (alanine); oxaloacetate (aspartate). Important transaminases: Aspartate transaminase (AST)
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Summary of Protein and Amino Acid Metabolism
(transaminase) Transamination Common acceptors: -ketoglutarate (glutamate) pyruvate (alanine); oxaloacetate (aspartate) Important transaminases: Aspartate transaminase (AST) (also called glutamate-oxaloacetate transaminase, GOT) High activity in heart; tool for diagnosis of heart damage Alanine transaminase (ALT) (also called glutamate-pyruvate transaminase, GPT) High activity in liver; tool for diagnosis of liver damage
Alanine – Glucose Cycle
O H2N C OPO32– -ketoglutarate carbamoyl phosphate -ketoglutarate glutamate malate NAD+ malate NADH pyruvate -ketoglutarate oxaloacetate aspartate aspartate glutamate NH4+ HCO3– citrulline ATP 2 ATP glutamine H2O citrulline 2Pi AMP Pi 2 ADP + Pi arginosuccinate fumarate H2O arginine ornithine O H2NCNH2 urea The Urea Cycle alanine (from muscle) glutamine (from extrahepatic tissues) cytosol ornithine mitochondrial matrix cytosol
Tryptophan Fate of Carbon Atoms from Amino Acids glucogenic amino acids ketogenic amino acids
Methionine (essential amino acid) Biosynthesis of Nonessential Amino Acids
Glycine Heme, Purines Tyrosine Thyroid Hormones Epinephrine Dopamine Melanin Histidine Aspartate Histamine Purines, Pyrimidines Tryptophan Glutamate Seratonin GABA (gamma-aminobutyrate) Amino Acid Product(s) Amino Acids as Precursors of Other Nitrogeneous Compounds