Description
A pyridoxal-phosphate protein. This enzyme catalyses the second step in the phosphorylated pathway of serine biosynthesis in Escherichia coli. It also catalyses the third step in the biosynthesis of the coenzyme pyridoxal 5'-phosphate in Escherichia coli (using Reaction 2 above). In Escherichia coli, pyridoxal 5'-phosphate is synthesized de novo by a pathway that involves EC 1.2.1.72 (erythrose-4-phosphate dehydrogenase), EC 1.1.1.290 (4-phosphoerythronate dehydrogenase), EC 2.6.1.52 (phosphoserine transaminase), EC 1.1.1.262 (4-hydroxythreonine-4-phosphate dehydrogenase), EC 2.6.99.2 (pyridoxine 5'-phosphate synthase) and EC 1.4.3.5 (with pyridoxine 5'-phosphate as substrate). Pyridoxal phosphate is the cofactor for both activities and therefore seems to be involved in its own biosynthesis. Non-phosphorylated forms of serine and threonine are not substrates