InterPro domain: IPR022278

Phosphoserine aminotransferase (PSAT) is involved in serine biosynthesis [ 1 , 2 ]. The enzyme catalyses the reversible conversion of 3-phosphohydroxypyruvate to L-phosphoserine. PSAT from Escherichia coli has been shown to be a homodimer of Mr79,000 with a conserved lysine that binds covalently to pyridoxal phosphate (PLP). PSAT is a vitamin B6-dependent enzyme and belongs to the alpha family of PLP enzymes. PSAT is also classified as a member of the aspartate aminotransferase family of PLP enzymes [ 3 ]. According to the structural classification of PLP-dependent enzymes [ 4 ], PSAT belongs to the pyridoxal phosphate (PLP)-dependent aspartate aminotransferase superfamily (fold I), where it is allocated to a separated subclass. The mechanism of action in all these enzymes is similar: PLP combines with an alpha-amino acid to form a compound called a Schiff base or aldimine intermediate, which, depending on the reaction, is the substrate in four kinds of reactions: transamination (movement of amino groups), racemization (redistribution of enantiomers), decarboxylation (removing COOH groups), and various side-chain reactions depending on the enzyme involved.

1. Dysregulation of serine biosynthesis contributes to the growth defect of a Mycobacterium tuberculosis crp mutant. Mol. Microbiol. 82, 180-98
2. Biochemical and functional characterization of phosphoserine aminotransferase from Entamoeba histolytica, which possesses both phosphorylated and non-phosphorylated serine metabolic pathways. Mol. Biochem. Parasitol. 145, 71-83
3. Structure, evolution and action of vitamin B6-dependent enzymes. Curr. Opin. Struct. Biol. 8, 759-69
4. Modeling of the spatial structure of eukaryotic ornithine decarboxylases. Protein Sci. 4, 1291-304