Catalyzes the reversible oxidation of 3-phospho-D-glycerate to 3-phosphonooxypyruvate, the first step of the phosphorylated L-serine biosynthesis pathway. Also catalyzes the reversible oxidation of 2-hydroxyglutarate to 2-oxoglutarate. (2R)-3-phosphoglycerate + NAD(+) = 3-phosphooxypyruvate + H(+) + NADH (R)-2-hydroxyglutarate + NAD(+) = 2-oxoglutarate + H(+) + NADH Displays feedback inhibition by L-serine. Inhibited by glycine. kcat is 0.55 sec(-1) for 3-phospho-D-glycerate oxidation. kcat is 27.8 sec(-1) for 3-phosphonooxypyruvate reduction. kcat is 33.3 sec(-1) for 2-oxoglutarate reduction. kcat is 0.71 sec(-1) for (R)-2-hydroxyglutarate oxidation. kcat is 0.25 sec(-1) for (S)-2-hydroxyglutarate oxidation. Optimum pH is 8.5 for the reductase activities and 9.0 for the dehydrogenase activities. Amino-acid biosynthesis; L-serine biosynthesis; L-serine from 3-phospho-D-glycerate: step 1/3. Homotetramer. Belongs to the D-isomer specific 2-hydroxyacid dehydrogenase family.