Synthesis of divinyl protochlorophyllide. Enzymological properties of the Mg-protoporphyrin IX monomethyl ester oxidative cyclase system.
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The resolution and reconstitution of the Mg-protoporphyrin IX monomethyl ester oxidative cyclase system into a supernatant and a pellet fraction was accomplished by a procedure involving salt treatment followed by osmotic shock. Recombination of pellet and supernatant fractions was required for cyclase activity. This restoration effect could be demonstrated using either Mg-protoporphyrin IX or Mg-protoporphyrin IX monomethyl ester as the cyclase substrate in the presence or absence of S-adenosylmethionine. Pretreatment of the pellet fraction with either 8-hydroxyquinoline or desferal mesylate inhibited cyclase activity, indicating that there is a heavy-metal-ion requirement in this fraction. The cyclase supernatant protein(s) was not internalized by Sephadex G-50 and did not bind to Blue Sepharose, suggesting that it has a molecular mass of over 30 kDa and that it does not bind the cofactor NADPH. The cyclase supernatant protein did bind to MgProtoMe2-bound Sepharose and could be eluted by raising the pH to 9.7 in the presence of 4 mM-n-octyl glucoside. The pH optimum of the cyclase was 9.0. About a 40-fold purification of the cyclase supernatant protein was achieved by a combination of (NH4)2SO4 fractionation and phenyl-Sepharose chromatography. (+info)
Nuclear quantum tunneling in the light-activated enzyme protochlorophyllide oxidoreductase.
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Pathways of formation of pigment forms at the terminal photobiochemical stage of chlorophyll biosynthesis.
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The pathways of transformation of the chromophore of pigment-protein complexes have been studied at the terminal light-dependent stage of chlorophyll biosynthesis in plant leaves. The overall scheme of the sequence of photochemical and dark reactions of the pigment chromophore initiated by the reaction of photochemical hydration of a molecule of the precursor (protochlorophyllide) is presented. Schemes of the transformations of the components of the photoactive protochlorophyllide-oxidoreductase complex are discussed. Data are presented of features of the process at different stages of the formation of the pigment apparatus of plants. (+info)
Divinyl chlorophyll(ide) a can be converted to monovinyl chlorophyll(ide) a by a divinyl reductase in rice.
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