Localization of Mg-Chelatase and Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase Activities within Isolated, Developing Cucumber Chloroplasts.

Magnesium chelatase and magnesium protoporphyrin IX monomethyl ester (oxidative) cyclase activities were both sensitive to inhibition by p-chloromercuribenzoate in intact, developing cucumber (Cucumis sativus L. var Beit Alpha) chloroplasts. Magnesium chelatase was also sensitive to the membrane-impermeable mercurial p-chloromercuribenzene sulfonate (PCMBS), while cyclase activity was only slightly sensitive.

Separation of Mg-Protoporphyrin IX and Mg-Protoporphyrin IX Monomethyl Ester Synthesized de novo by Developing Cucumber Etioplasts.

High pressure liquid chromatography was used to demonstrate that chelation of Mg(2+) into protoporphyrin IX precedes methylation in isolated greening etioplasts from cucumber (Cucumis sativus L. var. Beit Alpha) cotyledons.

Properties of Magnesium Chelatase in Greening Etioplasts: METAL ION SPECIFICITY AND EFFECT OF SUBSTRATE CONCENTRATIONS.

Evidence was obtained by means of low temperature spectrofluorimetry and high pressure liquid chromatography for the exclusive chelation of Mg(2+) into protoporphyrin IX by a plastid preparation extracted from greening cucumber cotyledons. Under the experimental conditions which were optimized for Mg(2+) chelation, Zn(2+) chelation was not detected. However, Zn(2+) chelation was observed when ATP was omitted and ZnCl(2) was added to the incubation mixture.