Glyceraldehyde 3-Phosphate Dehydrogenases and Glyoxylate Reductase

Ammonium sulfate chromatography has been employed to separate glyceraldehyde 3-phosphate dehydrogenases (GPD) of Sinapis alba cotyledons of various developmental stages. Cotyledons of dark-grown seedlings possess one major NAD-specific enzyme designated NAD-GPD I. Irradiation with continuous far red light leads to a strong increase in NADP-GPD activity and to the formation of a second NAD activity designated NAD-GPD II. These two activities occur in a constant ratio during cotyledon development, and they are eluted together in ammonium sulfate chromatography. In a later stage of cotyledon development the light-dependent increase in NAD-GPD II is matched by an equivalent decrease in NAD-GPD I. These data suggest that the chloroplast marker enzyme NADP-GPD (EC 1.2.1.13) also has NAD activity and that the light-dependent formation of this bifunctional enzyme is correlated with activity changes of the NAD-GPD of cytoplasmic glycolysis (EC 1.2.1.12).