This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: methyl ketone biosynthesis
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis|
|Generation of Precursor Metabolites and Energy|
Expected Taxonomic Range: Solanum
2-tridecanone is an aliphatic methyl ketone that is naturally occurring in plants, where it can play a role as both a pheromone and insecticide [Antonious03]. The methyl ketone biosynthetic pathway was characterized in tomato plants, specifically Solanum habrochaites, from which two key genes ShMKS1 and ShMKS2 were identified that were required for methyl ketone synthesis from fatty acid intermediates [Yu10a]. ShMKS1 is purported to hydrolyze a β-ketoacyl ACP to generate a β-keto acid, and ShMKS2 may decarboxylate the β-keto acid to a methyl ketone. More specifically, ShMKS2 and ShMKS1, heterologously expressed in E. coli and shown to work in sequence produced a variety of 2-methylketones such as 2-tridecanone, 2-undecanone and 2-pentadecanone [Fridman05, Yu10a, BenIsrael09].
The (C7- C15) methylketones are natural insecticides/pesticides and the biochemical pathways underlying the production of these toxins have been studied in tomato plants [Fridman05]. Solanum habrochaites accumulates methyl ketones in specific glandular trichomes and these cause mortality to insect pests such as the spider mites. Methyl ketones (MK) are abundantly present in the wild species Lycospersicum hirsutum (synonym Solanum habrochaites) and in significant lower concentrations in the domesticated species Solanum lycopersicum [Fridman05] which has prompted research that made those species the subject of breeding experiments to isolate the respective genes and improve the defense mechanism in the cultivated varieties [Chatzivasileiad99]. Interspecific populations derived from crosses of wild and cultivated tomato species were used and experiments were carried out to analyze the morphological basis for accumulation of MK's in certain types of trichomes as well as to study the chemical composition of the methylketones. The wild-type species had larger numbers of Type VI glandular trichomes on the leaf surfaces where methylketones accumulated. The cultivated species had fewer such trichomes and almost no accumulation of MK's of chain length C7 -C15.
With application to biofuel production, this pathway has recently been engineered into E.coli to overproduce saturated and monounsaturated C11- C15 methyl ketones, see methyl ketone biosynthesis [Goh12].
BenIsrael09: Ben-Israel I, Yu G, Austin MB, Bhuiyan N, Auldridge M, Nguyen T, Schauvinhold I, Noel JP, Pichersky E, Fridman E (2009). "Multiple biochemical and morphological factors underlie the production of methylketones in tomato trichomes." Plant Physiol 151(4);1952-64. PMID: 19801397
Chatzivasileiad99: Chatzivasileiadis EA, Boon JJ, Sabelis MW (1999). "Accumulation and turnover of 2-tridecanone in Tetranychus urticae and its consequences for resistance of wild and cultivated tomatoes." Exp Appl Acarol 23(12);1011-21. PMID: 10737735
Fridman05: Fridman E, Wang J, Iijima Y, Froehlich JE, Gang DR, Ohlrogge J, Pichersky E (2005). "Metabolic, genomic, and biochemical analyses of glandular trichomes from the wild tomato species Lycopersicon hirsutum identify a key enzyme in the biosynthesis of methylketones." Plant Cell 17(4);1252-67. PMID: 15772286
Yu10a: Yu G, Nguyen TT, Guo Y, Schauvinhold I, Auldridge ME, Bhuiyan N, Ben-Israel I, Iijima Y, Fridman E, Noel JP, Pichersky E (2010). "Enzymatic functions of wild tomato methylketone synthases 1 and 2." Plant Physiol 154(1);67-77. PMID: 20605911
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