Abstract
Washed cells of Rhodopseudomonas spheroides when suspended in a simple medium excreted magnesium protoporphyrin monomethyl ester. Addition of 8-hydroxyquinoline and copper to the suspending medium led to the excretion of pigments more closely related to chlorophyll, the nature of which depended upon the substrate provided. When α-oxoglutarate was supplied the main pigment was at the oxidation level of chlorophyll; when succinate was supplied, the main pigment was at the oxidation level of protochlorophyll. Malonate increased the tendency to accumulate the less reduced pigment at the protochlorophyll oxidation level. The possibility that the biosynthesis of chlorophyll in R. spheroides is dependent upon the availability of NADH is discussed. Extracts of R. spheroides catalysed the incorporation of Cu 2+ into porphyrins: the rate of copper porphyrin formation was increased by the addition of 8-hydroxyquinoline. The possibility that this reaction is implicated in the inhibitory action of copper-8-hydroxyquinoline complexes is also discussed.
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