Effect of growth conditions on the activation and inactivation of citrate lyase of Rhodopseudomonas gelatinosa.

Cells of Rhodopseudomonas gelatinosa growing with citrate anaerobically in the light contained citrate lyase only in the acetylated, enzymatically active form of this enzyme. After exhaustion of citrate in the culture medium citrate lyase was deacetylated to yield the inactive sulfhydryl (HS) enzyme. Acetylation of HS-citrate lyase required light, anaerobic conditions and the availability of citrate as substrate. The acetylation reaction already in progress stopped immediately when the culture was placed in the dark. Deacetylation of citrate lyase occurred anaerobically in the light when citrate was exhausted and under aerobic conditions in the presence or absence of citrate. In cells of R. gelatinosa fermenting citrate in the dark neither the acetylating enzyme nor the deacetylating enzyme was active.