Control of Triosephosphate Dehydrogenase in Photosynthesis

Abstract

The intracellular and phylogenetic distribution of the NAD and the NADP dependent triosephosphate dehydrogenases (TPD) in photosynthetic organisms has been examined in many laboratories (8,11,12, 20, 22). Studies by Fuller and Gibbs (6), and Smillie and Fuller (21) have indicated that the NADP enzyme occurs only in green tissues of higher plants and in O2 evolving photosynthetic microorganisms. Brawerman and Konigsberg (4) have studied the kinetics of the formation of the NADP enzyme in Euglena and found that the rates of synthesis of chlorophyll and the increase in NADP activity are approximately equal. These results led to the suggestion that the NADP enzyme functions in photosynthetic metabolism while the NAD enzyme is operative in oxidative or glycolytic metabolism. This suggestion received further support from the demonstration by Heber, Pon and Heber (12) that the NAD linked TPD is confined to the chloroplast in several higher plant species. In contrast to these findings, however, no NADP dependent TPD activity has been observed in photosynthetic bacteria (6,7). To examilne further the question of pyridinie niucleotide specificity in photosynthesis, we have studied the kinetics of changes in NADP and NAD linked dependent TPD activities in bleaching and regreening cultures of Chlamtdomonas reinhardi and Euglenta gracilis, and the activity and properties of the NAD dependent TPD from Chromatium strain D grown under either photolithotrophic or photoorganotrophic conditions.