Compartmentation of glycolysis and of the oxidative pentose-phosphate pathway in Chlamydomonas reinhardii

Abstract

Glycolytic enzyme activities and enzyme activities of the oxidative pentose-phosphate pathway were measured in intact chloroplasts from Chlamydomonas reinhardii. By comparison with the total enzyme activities of intact protoplasts of the alga the data were used to locate these enzymes quantitatively in the algal chloroplast. It was found that the glycolytic chain in C. reinhardii is roughly split into a plastidic and an extraplastidic part. More than 90% of the first part of glycolysis (from fructose-6-phosphate to triose-phosphate is located in the plastid while more than 95% of the second part (from glycerate-3-phosphate to pyruvate) is outside. Around 70% of glucose-6-phosphate dehydrogenase and gluconate-6-phosphate dehydrogenase, two key enzymes of the oxidative pentose phosphate pathway, are located in the plastid. It is concluded that in C. reinhardii the major part of hexose breakdown to triose-phosphate occurs in the chloroplast and that a tight cooperation between the plastid and the cytoplasm is required for appreciable sugar breakdown to occur in the algal cell.