Question

Describe the role of PLP in the biosynthesis of serine, glycine and cysteine

Answer 1

Pyridoxal 5'-phosphate enzymes are ubiquitous in the nitrogen metabolism of all organisms. They catalyze a wide variety of reactions including racemization, transamination, decarboxylation, elimination, retro-aldol cleavage, Claisen condensation, and others on substrates containing an amino group, most commonly α-amino acids.

the carbanionic intermediate can act as a nucleophile. This occurs in aldol and Claisen condensation reactions that occur in amino acid metabolism]

If there is a good leaving group present at Cβ it can be lost from the carbanionic intermediate to form an aminoacrylate intermediate. This α–β elimination reaction is central to the biosynthesis of tryptophan, cysteine, and other metabolites