Involved in the plastidial phosphorylated pathway of serine biosynthesis (PPSB). Required for mature pollen development. (2R)-3-phosphoglycerate + NAD(+) = 3-phosphooxypyruvate + H(+) + NADH Partially inhibited by 5 mM serine. Amino-acid biosynthesis; L-serine biosynthesis; L-serine from 3-phospho-D-glycerate: step 1/3. Ubiquitous, but highly expressed in roots. Expressed in vasculature, root and shoot meristems, distal part of cotyledons and leaves, anther, stigma and pollen grains. Detected at the tip of the cotyledons in late embryos. Up-regulated in the aerial parts by dark treatment, high CO(2) levels and necrotrophic pathogen infection. Embryo lethal when homozygous. Belongs to the D-isomer specific 2-hydroxyacid dehydrogenase family.