Resolution and Reconstitution of Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase, the Enzyme System Responsible for the Formation of the Chlorophyll Isocyclic Ring.

Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase, the system responsible for the formation of the chlorophyll isocyclic ring in developing cucumber (Cucumis sativus L. cv Beit Alpha) chloroplasts, was resolved into two enzymic components: a high-speed supernatant and a membrane pellet. This reconstituted enzyme system required reduced pyridine nucleotide for activity.