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