Variations of SGAT enzymes activity of Chlamydomonas reinhardtii cells under different cultural conditions.

In this study, the model single cell plant Chlamydomonas reinhardtii was used to investigate varia- tions in serine: glyoxylate aminotransferase activity in cells under different cultural conditions. The results showed the optimum pH of SGAT was in the range of 5–7, and SGAT decreased gradually when the pH was higher than 7. SGAT activity in the cell also declined with the increase of cell density. SGAT activity was influenced significantly by the light intensity, and the effect strengthened with the increase of light intensity. Moreover, acetate, which was the sole carbon source of C. reinhardtii in heterotrophic growth, also affected the SGAT activity. In addition, SGAT activity in the cell increased remarkably when the oxygen concentration was higher than that in the normal air, and the increased carbon dioxide concentration treatment also led to an increase. The SGAT activity both reduced under 40 or 15 ℃. Furthermore, the content of Gly was increased and the content of Ser was decreased when the oxygen pressure increased in the air, resulting in a raise in Gly/ Ser ratio from 0.79 to 1.49.