RESUMO
The high level of delta-aminolaevulinate synthetase (ALA-S) in Rhodopseudomonas palustris cells grown under photosynthetic conditions decreased when they were vigorously aerated; moreover, the bacteriochlorophyll synthesis suddenly stopped. When aeration was interrupted, enzymatic level increased notably, but bacteriochlorophyll level did not. Chloramphenicol added to cultures when aeration was interrupted did not affect the increase of enzymic level. When it was added as the aeration started, the enzymic level decayed, but did not increase as notably when the aeration was interrupted. ALA-S in extracts of aerated cells underwent spontaneous activation when homogenates were stored at 4 degrees C. The effect of several activators on different forms of ALA-S is postulated in order to explain these findings.