Effects of Iron and Oxygen on Chlorophyll Biosynthesis : II. OBSERVATIONS ON THE BIOSYNTHETIC PATHWAY IN ISOLATED ETIOCHLOROPLASTS.
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.
Chereskin
B M
BM
Department of Botany, University of California, Davis, California 95616.
Castelfranco
P A
PA