α-Keto acid elongation and glucosinolate biosynthesis in Arabidopsis thaliana

Campos, Hugo; Magrath, R.; McCallum, Don G.; Kroymann, Juergen; Scnabelrauch, D.; Mitchell-Olds, Thomas; Mithen, Richard

doi:10.1007/s001220051500

Cited by 78 publications

(61 citation statements)

References 13 publications

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“…GSLs were extracted from 300 mg of seeds, converted to desulphoglucosinolates, and analyzed by LC-MS with atmospheric pressure chemical ionization, as previously described (de Quiros et al, 2000).…”

Section: Gsl Analysismentioning

confidence: 99%

“…In addition, all ecotypes produce similar amounts of long chain GSLs in leaves and seeds, derived from four, five, and six rounds of Met elongation. The variation in 3C to 4C ratio is determined by alleles at the Gsl-elong locus on chromosome 5 (de Quiros et al, 2000;Kroymann et al, 2001). In Col-0, this locus contained two genes, MAM1 (At5g23020) and MAML (At5g23010), which have high levels of homology to isopropylmalate synthase (IPMS; EC 2.3.3.13) that catalyzes acetyl CoA-oxo acid condensation in Leu biosynthesis.…”

mentioning

confidence: 99%

“…In addition to determining the ratio of 3C to 4C chain lengths, the Gsl-elong locus functions as a quantitative trait locus determining overall levels of Metderived GSLs (de Quiros et al, 2000;Kroymann et al, 2001), similar to a quantitative trait locus in Brassica that determines both 3C to 4C ratio and total amounts (Mithen et al, 2003). Fine mapping and sequence analysis in several Arabidopsis ecotypes reveal that the Gsl-elong locus comprises, in addition to MAM1 and MAML, a further gene designated MAM2.…”

mentioning

confidence: 99%

“…1c); they all have highly conserved domains near the amino terminus which are signatures of the active site for oxo acid condensation reactions (Evans et al, 1991;de Quiros et al, 2000) as well as strong overall similarity to IPMS and homocitrate synthase (EC 2.3.3.14), which catalyze such condensation reactions in yeast and bacteria (Fig. 1c).…”

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confidence: 99%

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Glucosinolate and Amino Acid Biosynthesis in Arabidopsis

et al. 2004

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Enzymes that catalyze the condensation of acetyl coenzyme A and 2-oxo acids are likely to be important in two distinct metabolic pathways in Arabidopsis. These are the synthesis of isopropylmalate, an intermediate of Leu biosynthesis in primary metabolism, and the synthesis of methylthioalkylmalates, intermediates of Met elongation in the synthesis of aliphatic glucosinolates (GSLs), in secondary metabolism. Four Arabidopsis genes in the ecotype Columbia potentially encode proteins that could catalyze these reactions. MAM1 and MAML are adjacent genes on chromosome 5 at the Gsl-elong locus, while MAML-3 and MAML-4 are at opposite ends of chr 1. The isopropylmalate synthase activity of each member of the MAM-like gene family was investigated by heterologous expression in an isopropylmalate synthase-null Escherichia coli mutant. Only the expression of MAML-3 restored the ability of the mutant to grow in the absence of Leu. A MAML knockout line (KO) lacked long-chain aliphatic GSLs, which were restored when the KO was transformed with a functional MAML gene. Variation in expression of MAML did not alter the total levels of Met-derived GSLs, but just the ratio of chain lengths. MAML overexpression in Columbia led to an increase in long-chain GSLs, and an increase in 3C GSLs. Moreover, plants overexpressing MAML contained at least two novel amino acids. One of these was positively identified via MS/MS as homo-Leu, while the other, with identical mass and fragmentation patterns, was likely to be homo-Ile. A MAML-4 KO did not exhibit any changes in GSL profile, but had perturbed soluble amino acid content.

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Section: Gsl Analysismentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Glucosinolate and Amino Acid Biosynthesis in Arabidopsis

et al. 2004

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“…A principal reason for this attention is the potential role of these genes in glucosinolate biosynthesis. Two of these IPMS-like sequences (At5g23010 and Atg5g23020) are located at the GS-Elong locus on chromosome V, which regulates the side-chain length of the aliphatic glucosinolates in Arabidopsis (Campos de Quiros et al, 2000;Kroymann et al, 2001Kroymann et al, , 2003.…”

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confidence: 99%

Two Arabidopsis Genes (IPMS1 and IPMS2) Encode Isopropylmalate Synthase, the Branchpoint Step in the Biosynthesis of Leucine

et al. 2006

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Heterologous expression of the Arabidopsis (Arabidopsis thaliana) IPMS1 (At1g18500) and IPMS2 (At1g74040) cDNAs in Escherichia coli yields isopropylmalate synthases (IPMSs; EC 2.3.3.13). These enzymes catalyze the first dedicated step in leucine (Leu) biosynthesis, an aldol-type condensation of acetyl-coenzyme A (CoA) and 2-oxoisovalerate yielding isopropylmalate. Most biochemical properties of IPMS1 and IPMS2 are similar: broad pH optimum around pH 8.5, Mg 21 as cofactor, feedback inhibition by Leu, K m for 2-oxoisovalerate of approximately 300 mM, and a V max of approximately 2 3 10 3 mmol min 21 g 21 . However, IPMS1 and IPMS2 differ in their K m for acetyl-CoA (45 mM and 16 mM, respectively) and apparent quaternary structure (dimer and tetramer, respectively). A knockout insertion mutant for IPMS1 showed an increase in valine content but no changes in Leu content; two insertion mutants for IPMS2 did not show any changes in soluble amino acid content. Apparently, in planta each gene can adequately compensate for the absence of the other, consistent with available microarray and reverse transcription-polymerase chain reaction data that show that both genes are expressed in all organs at all developmental stages. Both encoded proteins accept 2-oxo acid substrates in vitro ranging in length from glyoxylate to 2-oxohexanoate, and catalyze at a low rate the condensation of acetyl-CoA and 4-methylthio-2-oxobutyrate, i.e. a reaction involved in glucosinolate chain elongation normally catalyzed by methylthioalkylmalate synthases. The evolutionary relationship between IPMS and methylthioalkylmalate synthase enzymes is discussed in view of their amino acid sequence identity (60%) and overlap in substrate specificity.

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Glucosinolates inBrassicavegetables: The influence of the food supply chain on intake, bioavailability and human health

Verkerk¹,

Schreiner

Krumbein

et al. 2009

Molecular Nutrition Food Res

517

424

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Glucosinolates (GLSs) are found in Brassica vegetables. Examples of these sources include cabbage, Brussels sprouts, broccoli, cauliflower and various root vegetables (e.g. radish and turnip). A number of epidemiological studies have identified an inverse association between consumption of these vegetables and the risk of colon and rectal cancer. Animal studies have shown changes in enzyme activities and DNA damage resulting from consumption of Brassica vegetables or isothiocyanates, the breakdown products (BDP) of GLSs in the body. Mechanistic studies have begun to identify the ways in which the compounds may exert their protective action but the relevance of these studies to protective effects in the human alimentary tract is as yet unproven. In vitro studies with a number of specific isothiocyanates have suggested mechanisms that might be the basis of their chemoprotective effects. The concentration and composition of the GLSs in different plants, but also within a plant (e.g. in the seeds, roots or leaves), can vary greatly and also changes during plant development. Furthermore, the effects of various factors in the supply chain of Brassica vegetables including breeding, cultivation, storage and processing on intake and bioavailability of GLSs are extensively discussed in this paper.

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α-Keto acid elongation and glucosinolate biosynthesis in Arabidopsis thaliana

Cited by 78 publications

References 13 publications

Glucosinolate and Amino Acid Biosynthesis in Arabidopsis

Glucosinolate and Amino Acid Biosynthesis in Arabidopsis

Two Arabidopsis Genes (IPMS1 and IPMS2) Encode Isopropylmalate Synthase, the Branchpoint Step in the Biosynthesis of Leucine

Glucosinolates inBrassicavegetables: The influence of the food supply chain on intake, bioavailability and human health

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