Biosynthesis of the NutritionallyNonessential Amino Acids

BIOMEDICAL IMPORTANCE

• Amino acids present in proteins• Amino acid deficiency– Kwashiorkor – Marasmus• Caloric intake & specific amino acids are deficient

• Humans can synthesize 12 of the 20 common amino acids from the amphibolic intermediates

Amino acid requirements of humans

• amino acids from – Amphibolic intermediates• α-ketoglutarate• Oxaloacetate • 3-phosphoglycerate

– Dietary amino acids

The glutamate dehydrogenasereaction

Formation of alanine by transaminationof pyruvate

The asparagine synthetase reaction

The glutamine synthetase reaction

Serine biosynthesis

Formation of glycine from choline

The serine hydroxymethyltransferasereaction

Biosynthesis of proline from glutamate

Conversion of homocysteine and serine to homoserine and cysteine

The phenylalanine hydroxylase reaction

The prolyl hydroxylase reaction

Selenocysteine (top) and the reactioncatalyzed by selenophosphate synthetase (bottom)

• Selenocysteine-specific UGA codon• Selenocysteine insertion element

Catabolism of proteins

• Urea synthesis

Partial reactions in the attachment of ubiquitin (UB) to proteins.

Overall flow of nitrogen in amino acidcatabolism

Transamination

Alanine aminotransferase (top) andglutamate aminotransferase (bottom).

The L-glutamate dehydrogenase reaction

Oxidative deamination catalyzed byL-amino acid oxidase

The glutamine synthase reaction

The glutaminase reaction

Reactions and intermediates of urea biosynthesis

METABOLIC DISORDERS

• Hyperammonemia Type 1.• Hyperammonemia Type 2• Citrullinemia– argininosuccinate synthase

• Argininosuccinicaciduria– Argininosuccinase

• Hyperargininemia