(R)-glycerate + NAD(+) = 3-hydroxypyruvate + H(+) + NADH Photosynthesis; photorespiration; 3-phospho-D-glycerate from glycine: step 3/4. The appearance of HPR in the cotyledons of cucumber seedlings is both developmentally and light-regulated possibly at the level of transcription. Belongs to the D-isomer specific 2-hydroxyacid dehydrogenase family.