Pyruvate Carboxylase in Rhodopseudomonas spheroides

Abstract

SUMMARY: Unlike some other photosynthetic bacteria, Rhodopseudomonas spheroides directly carboxylates pyruvate in a reaction catalysed by a pyruvate carboxylase (E.C. 6.4.1.1). A partially purified preparation of the enzyme was acetylCoA-dependent. No phosphoenolpyruvate synthetase or phosphoenolpyruvate carboxylase activity was detected in extracts of R. spheroides. The organisms dependence upon its pyruvate carboxylase was shown by the fact that a mutant strain which lacked this enzyme was unable to grow either anaerobically in the light, or aerobically in the dark, on glucose or pyruvate (with CO2). Convenient spectrophotometric assays for pyruvate carboxylase are reported.