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The Chlorophyll Biosynthetic Enzyme Mg-Protoporphyrin Ix Monomethyl Ester (Oxidative) Cyclase (Characterization And Partial Purification From Chlamydomonas Reinhardtii And Synechocystis Sp. Pcc 6803), David Bollivar
David Bollivar
A universal structural feature of chlorophyll molecules is the isocyclic ring. This ring is formed by the action of the enzyme Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase, which catalyzes a complex reaction in which Mg-protoporphyrin IX monomethyl ester is converted to divinyl protochlorophyllide (also called Mg-2,4-divinylpheoporphyrin a5), with the participation of NADPH and O2. Cyclase activity was demonstrated in lysed Chlamydomonas reinhardtii chloroplasts and extracts of Synechocystis sp. PCC 6803. The yield of the reaction product was increased by the addition of catalase and ascorbate or isoascorbate to the incubation mixture. These compounds may act by preventing degradation of the …