Properties of the Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase System | Zendy

Yum-Shing Wong | Zendy; Paul A. Castelfranco | Zendy

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Properties of the Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase System

Author(s) -

Yum-Shing Wong,

Paul A. Castelfranco

Publication year - 1985

Publication title -

plant physiology

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 3.554

H-Index - 312

eISSN - 1532-2548

pISSN - 0032-0889

DOI - 10.1104/pp.79.3.730

Subject(s) - dithiothreitol , chemistry , propionate , oxidative phosphorylation , side chain , enzyme , substrate (aquarium) , sodium arsenite , stereochemistry , biochemistry , organic chemistry , oceanography , arsenic , geology , polymer

Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase, the enzyme system responsible for the formation of the chlorophyll isocyclic ring, exhibits requirements for both essential sulfhydryls and essential disulfides. It is inhibited by N-ethylmaleimide, dithiothreitol, and beta-mercaptoethanol, but not by sodium arsenite. This enzyme system shows some substrate specificity: (a) the 6-side-chain of the macrocycle can either be a methyl propionate ester, or its beta-hydroxy or beta-keto derivatives; (b) the 7-side-chain can either be a propionic acid or a methyl propionate ester; (c) both the 4-vinyl and the 4-ethyl series can serve as substrates, at least at the beta-keto ester level; (d) the activity appears to be lost if the side-chain in the 2-position is reduced from a vinyl to an ethyl.

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