Amino Acid Metabolism Essential Amino Acids Essential amino
Amino Acid Metabolism
Essential Amino Acids Essential amino acids must be consumed in the diet. Mammalian cells lack enzymes to synthesize their carbon skeletons (a-keto acids). These include: Isoleucine, & valine Lysine Threonine Tryptophan Phenylalanine (Tyr can be made from Phe. ) Methionine (Cys can be made from Met. ) Histidine (Essential for infants. )
Reductive amination catalyzed by glutamate dehydrogenase
Glutamine synthesis is coupled to hydrolysis of ATP
Pyruvate is an amphibolic intermediate in synthesis of alanine
Asparagine synthesis is energetically favorable due to coupling to ATP hydrolysis
Serine biosynthesis
Multistep pathway for glycine biosynthesis
Glycine is also synthesized from serine
Proline biosynthesis
Cysteine is not nutritionally essential, however it is derived from methionine
Tyrosine is formed from phenylalanine
Hydroxyproline is formed after protein synthesis
Selenocysteine is synthesized from serine and selenophosphate
Amino acids that are synthesized de novo in humans. All are related by a small number of steps to glycolysis or TCA cycle intermediates.
Salvage pathways formation of certain nonessential amino acids from other amino acids Amino Acid formed Precursor Amino Acid Arginine Proline Cysteine Methionine Tyrosine Phenylalanine
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