Periodic increases in enzyme activity in synchronized cultures of Chlamydomonas reinhardtii

Abstract

During synchronized growth of Chlamydomonas reinhardtii on a 12-h light-12-h dark cycle, net protein synthesis occurs approximately linearly in the light period but no appreciable increase is observed during the dark period of growth. Increases in activity of alanine dehydrogenase ( l-alanine:NAD oxidoreductase, EC 1.4.1.1), glutamate dehydrogenase ( l-glutamate:NAD(P) oxidoreductase, EC 1.4.1.3), phosphoenolpyruvate carboxylase (orthophosphate:oxaloacetate carboxylyase (phosphorylating), EC 4.1.1.31), aspartate carbamoyltransferase (carbamoylphosphate: l-aspartate carbamoyltransferase, EC 2.1.3.2) and ornithine carbamoyltransferase (carbamoylphosphate: l-ornithine carbamoyl transferase, EC 2.1.3.3) occur within characteristic periods of time during the life cycle of the cell. The activity of alanine dehydrogenase and aspartate carbamoyltransferase increases primarily in the light period, whereas the activity of the other three enzymes increases during the dark period of growth.