Biosynthesis of methionine-derived glucosinolates in Arabidopsis thaliana: Recombinant expression and characterization of methylthioalkylmalate synthase, the condensing enzyme of the chain-elongation cycle

Textor, Susanne, Bartram, Stefan, Kroymann, Jürgen, Falk, Kimberly L., Hick, Alastair, Pickett, John A. ORCID: https://orcid.org/0000-0002-8386-3770 and Gershenzon, Jonathan 2004. Biosynthesis of methionine-derived glucosinolates in Arabidopsis thaliana: Recombinant expression and characterization of methylthioalkylmalate synthase, the condensing enzyme of the chain-elongation cycle. Planta 218 (6) , pp. 1026-1035. 10.1007/s00425-003-1184-3

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Abstract

The major class of glucosinolates in Arabidopsis thaliana (L.) Heynh. are biosynthesized from methionine involving a three-step chain-elongation cycle. Each passage through the cycle results in the net addition of a single methylene group, with up to six cycles of elongation occurring in A. thaliana. The first reaction of the cycle is catalyzed by a methylthioalkylmalate synthase (MAMS), which condenses a ω-methylthio-2-oxoalkanoic acid with acetyl-CoA. Here we have demonstrated that MAM1, one of two similar genes in the A. thaliana ecotype Columbia, encodes a MAMS catalyzing the condensing reactions of the first two elongation cycles but not those of further cycles. The Columbia ecotype is dominated by compounds that have undergone only two elongation cycles. The A. thaliana MAM1 protein exhibits basic sequence similarity to other previously described enzymes catalyzing the condensation of 2-oxo acids and acetyl-CoA, such as isopropylmalate synthase (EC 2.3.3.13), an enzyme of leucine biosynthesis, and homocitrate synthase (EC 2.3.3.14). It also shares similar properties with them, including the catalytic requirements for a divalent metal ion and an adenine nucleotide. However, the MAM1 protein does not show activity with the substrates of any of these other enzymes, and was chromatographically separable from isopropylmalate synthase in extracts of A. thaliana. Thus, MAM1 is exclusively an enzyme of secondary metabolism, distinct from primary metabolic enzymes catalyzing similar reactions.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Chemistry
Publisher:	Springer
ISSN:	0032-0935
Date of Acceptance:	10 November 2003
Last Modified:	25 Feb 2026 15:00
URI:	https://orca.cardiff.ac.uk/id/eprint/185292

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