If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: methionine elongation
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Nitrogen-Containing Secondary Compounds Biosynthesis → Nitrogen-Containing Glucosides Biosynthesis → Glucosinolates Biosynthesis|
Some taxa known to possess this pathway include : Arabidopsis thaliana col
Expected Taxonomic Range: Brassicales
The biosynthesis of aliphatic glucosinolates is divided into three major stages, first the chain elongation of amino acids such as methionine (this pathway) and phenylalanine, followed by the core biosynthesis of the glucosinolates (compare glucosinolate biosynthesis from homomethionine) and finally secondary modifications of the glucosinolates [Wittstock02] [Halkier06].
The structural diversity of glucosinolates results from different precursor amino acids, varying length of the side chain and different patterns of secondary oxidation and esterification [Tokuhisa04]. Over 120 different glucosinolates have been described so far in plants [Fahey01]. Glucosinolates belong to one of the largest group of secondary metabolites found in the model plant Arabidopsis thaliana [DAuria05], where 39 glucosinolates have been identified in 34 different ecotypes indicating the plasticity of glucosinolate biosynthesis. A significant part of that diversity of aliphatic glucosinolates in Arabidopsis is based on varying side chain length [Kliebenstein01].
About This Pathway
The reaction sequence that is characteristic for the side chain elongation of methionine comprises three steps. Those reactions form a cycle which is repeatedly run through for the production of the C3 to C8 glucosinolates (the number of C refers to the number of methylene groups in the side chain) found in Arabidopsis [Textor07]. The first step is the condensation of acetyl-CoA with the deaminated 2-oxo-derivative of methionine, followed by the isomerization of the generated 2-malate derivative to form a 3-malate derivative which finally undergoes oxidative decarboxylation yielding a 2-oxo acid that is elongated by one more methylene group and can either reenter the cycle or proceed to the core biosynthetic steps [Halkier06].
This side chain elongation cycle very much resembles the reaction sequence being found in leucine biosynthesis. Therefore it was not surprising that enzymes of leucine biosynthesis also function in methionine chain elongation leading to glucosinolate biosynthesis, and vise versa [Knill08, Knill09, He09].
Unification Links: PlantCyc:PWYQT-4450
He09: He Y, Mawhinney TP, Preuss ML, Schroeder AC, Chen B, Abraham L, Jez JM, Chen S (2009). "A redox-active isopropylmalate dehydrogenase functions in the biosynthesis of glucosinolates and leucine in Arabidopsis." Plant J 60(4);679-90. PMID: 19674406
Heidel06: Heidel AJ, Clauss MJ, Kroymann J, Savolainen O, Mitchell-Olds T (2006). "Natural variation in MAM within and between populations of Arabidopsis lyrata determines glucosinolate phenotype." Genetics 173(3);1629-36. PMID: 16702431
Kliebenstein01: Kliebenstein DJ, Kroymann J, Brown P, Figuth A, Pedersen D, Gershenzon J, Mitchell-Olds T (2001). "Genetic control of natural variation in Arabidopsis glucosinolate accumulation." Plant Physiol 126(2);811-25. PMID: 11402209
Knill08: Knill T, Schuster J, Reichelt M, Gershenzon J, Binder S (2008). "Arabidopsis branched-chain aminotransferase 3 functions in both amino acid and glucosinolate biosynthesis." Plant Physiol 146(3);1028-39. PMID: 18162591
Knill09: Knill T, Reichelt M, Paetz C, Gershenzon J, Binder S (2009). "Arabidopsis thaliana encodes a bacterial-type heterodimeric isopropylmalate isomerase involved in both Leu biosynthesis and the Met chain elongation pathway of glucosinolate formation." Plant Mol Biol 71(3);227-39. PMID: 19597944
Kroymann01: Kroymann J, Textor S, Tokuhisa JG, Falk KL, Bartram S, Gershenzon J, Mitchell-Olds T (2001). "A gene controlling variation in Arabidopsis glucosinolate composition is part of the methionine chain elongation pathway." Plant Physiol 127(3);1077-88. PMID: 11706188
Textor04: Textor S, Bartram S, Kroymann J, Falk KL, Hick A, Pickett JA, Gershenzon J (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);1026-35. PMID: 14740211
Textor07: Textor S, de Kraker JW, Hause B, Gershenzon J, Tokuhisa JG (2007). "MAM3 catalyzes the formation of all aliphatic glucosinolate chain lengths in Arabidopsis." Plant Physiol 144(1);60-71. PMID: 17369439
Tokuhisa04: Tokuhisa J, de Kraker J-W, Textor S, Gershenzon J (2004). "The biochemical and molecular origins of aliphatic glucosinolate diversity in Arabidopsis thaliana." In: Secondary metabolism in model systems. Romeo JT (ed.). Recent advances in phytochemistry, Vol 38, 19-39.
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
Sawada09: Sawada Y, Kuwahara A, Nagano M, Narisawa T, Sakata A, Saito K, Hirai MY (2009). "Omics-based approaches to methionine side chain elongation in Arabidopsis: characterization of the genes encoding methylthioalkylmalate isomerase and methylthioalkylmalate dehydrogenase." Plant Cell Physiol 50(7);1181-90. PMID: 19493961
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