Transient kinetics of the reaction catalysed by magnesium protoporphyrin IX methyltransferase

Shepherd, Mark and Hunter, C. Neil (2004) Transient kinetics of the reaction catalysed by magnesium protoporphyrin IX methyltransferase. Biochemical Journal, 382 (Pt 3). pp. 1009-13. ISSN 0264-6021. (The full text of this publication is not available from this repository)

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Official URL
http://dx.doi.org/10.1042/BJ20040661

Abstract

Magnesium protoporphyrin IX methyltransferase (ChlM), an enzyme in the chlorophyll biosynthetic pathway, catalyses the transfer of a methyl group to magnesium protoporphyrin IX (MgP) to form magnesium protoporphyrin IX monomethyl ester (MgPME). S-Adenosyl-L-methionine is the other substrate, from which a methyl group is transferred to the propionate group on ring C of the porphyrin macrocycle. Stopped-flow techniques were used to characterize the binding of porphyrin substrate to ChlM from Synechocystis PCC6803 by monitoring tryptophan fluorescence quenching on a millisecond timescale. We concluded that a rapid binding step is preceded by a slower isomerization of the enzyme. Quenched-flow techniques have been employed to characterize subsequent partial reactions in the catalytic mechanism. A lag phase has been identified that has been attributed to the formation of an intermediate. Our results provide a greater understanding of this catalytic process which controls the relative concentrations of MgP and MgPME, both of which are implicated in signalling between the plastid and nucleus in plants.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Mark Shepherd
Date Deposited: 01 Sep 2011 16:11
Last Modified: 15 Apr 2014 07:53
Resource URI: http://kar.kent.ac.uk/id/eprint/28094 (The current URI for this page, for reference purposes)
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