Article
Mg-protoporphyrin IX monomethyl ester cyclase from Rhodobacter capsulatus: radical SAM-dependent synthesis of the isocyclic ring of bacteriochlorophylls
Biochemical Journal
(2020)
Abstract
During bacteriochlorophyll a biosynthesis, the oxygen-independent conversion of Mg-protoporphyrin IX monomethyl ester (Mg-PME) to protochlorophyllide (Pchlide) is catalyzed by the anaerobic Mg-PME cyclase termed BchE. Bioinformatics analyses in combination with pigment studies of cobalamin-requiring Rhodobacter capsulatus mutants indicated an unusual radical S-adenosylmethionine (SAM) and cobalamin-dependent BchE catalysis. However, in vitro biosynthesis of the isocyclic ring moiety of bacteriochlorophyll using purified recombinant BchE has never been demonstrated. We established a spectroscopic in vitro activity assay which was subsequently validated by HPLC analyses and H218O isotope label transfer onto the carbonyl-group (C-131-oxo) of the isocyclic ring of Pchlide. The reaction product was further converted to chlorophyllide in the presence of light-dependent Pchlide reductase.
Keywords
- BchE,
- chlorophyll,
- Mg-protoporphyrin IX monomethyl ester cyclase,
- radical SAM enzyme,
- Rhodobacter capsulatus
Disciplines
Publication Date
Winter December, 2020
DOI
https://doi.org/10.1042/BCJ20200761
Publisher Statement
Biochemical Journal is published by Portland Press. For more information about this journal please visit Portland Press online.
Citation Information
David Bollivar, Milan Wiesselmann, Stefanie Hebecker, José M Borrero-de Acuña, et al.. "Mg-protoporphyrin IX monomethyl ester cyclase from Rhodobacter capsulatus: radical SAM-dependent synthesis of the isocyclic ring of bacteriochlorophylls" Biochemical Journal Vol. 477 Iss. 23 (2020) p. 4635 - 4654 ISSN: 0264-6021 Available at: http://works.bepress.com/david_bollivar/31/