3-Phosphoglycerate dehydrogenase (PHGDH; EC 1.1.1.95) catalyzes the transition of 3-phosphoglycerate into 3-phosphohydroxypyruvate, which is the first and rate-limiting step in the phosphorylated pathway of serine biosynthesis, using NAD+/NADH as a cofactor. The deduced 533-amino acid protein, with a molecular mass of 56.8 kD, shares 94% sequence identity with rat liver 3-PGDH. Northern blot analysis detected a major 2.1-kb transcript at high levels in prostate, testis, ovary, brain, liver, kidn