The use of N-methylprotoporphyrin dimethyl ester to inhibit ferrochelatase in Rhodopseudomonas sphaeroides and its effect in promoting biosynthesis of magnesium tetrapyrroles

Publisher Website
Google Scholar
Abstract
N-methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membanes of R. sphaeroides at low concentrations (.apprx. 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of R. sphaeroides caused a decrease (.apprx. 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of heme into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent R. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylpheoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylpheophorbide a were excreted, with maximum efect at .apprx. 3 .mu.M inhibitor in the medium. Evidently, the inhibitor decreased concentration of intracellular heme which normally controls the activity of 5-aminolevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells.

This publication has 19 references indexed in Scilit: