The conversion of l-glutamate to delta-aminolevulinate, in preparations of cucumber etiochloroplasts incubated in vitro, was inhibited by protoheme IX and Mg-protoporphyrin IX. Mg-protoporphyrin IX was destroyed in the presence of air and plastids; this breakdown was accelerated by S-adenosyl methionine. Mg-protoporphyrin IX was also converted to protochlorophyllide in vitro. This conversion exhibited an absolute requirement for atmospheric oxygen and was strongly stimulated by S-adenosyl methionine and by darkness.Based on these results, and on the results of the preceding paper (Spiller, Castelfranco, Castelfranco 1981 Plant Physiol 68: 107-111), a comprehensive hypothesis for the role of O(2) and Fe in chlorophyll biosynthesis is formulated.
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Chereskin et al. (1982) studied this question.
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