| Popis: |
Two types of ALA synthetase, Fraction I and Fraction II, were estimated in the cells of R. spheroides 2 which were incubated at several different environmental conditions. ALA synthetase activity in the light-anaerobically grown cells was about three times higher than that in the dark-aerobically grown cells. The activity in the dark-aerobically grown cells increased by about three times when the cells were further incubated under low aeration in the dark for 3 hr. However, the marked increase in activity resulting from semianaerobic incubation was found in only Fraction I; the activity increase in Fraction II was insignificant. In contrast, when the cells were incubated under semianaerobic conditions in the light, the activities in both Fraction I and Fraction II were markedly increased. However, when the dark-aerobically grown cells were incubated for 3 hr under illumination and a high aeration, the activity in Fraction II was not increased. These results indicate that the synthesis of both Fraction I and Fraction II are repressed under a high partial pressure of oxygen and while Fraction I can be induced by the reduction of the oxygen tension alone, the induction of Fraction II requires illumination in addition to the reduction of oxygen tension. These findings suggest that R. spheroides has the two control systems for the ALA synthetase synthesis and the synthesis of Fraction I and Fraction II are controlled independently. |
