58 青葉アルコールの生合成(その4) : 緑葉中の"green香"生成機構とその周辺

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Leaf alcohol (cis-3-hexenol) and leaf aldehyde (trans-2-hexenal), which are formed from cis-3-hexenal, are widely distributed in fresh leaves, vegetables and fruits are responsible for "green odour" characteristic of leaves. We have demonstrated that the "green odour" (C_6-alcohols and -aldehydes) are biosynthesized by the enzymatic oxygenation (E'_2) and subsequent cleavage reaction (E"_2) from linolenic acid, which are liberated from phospholipid and neutral fats by acylhydlase in chloroplast. In this paper, we describe the stereoselective oxygenation to linoleic acid, the ester and linoleylalcohol, and 2) the mechanism of cleavage reaction to C_6-aldehyde and C_<12>-oxo-acid of 13-L-hydroperoxide, and 3) mutual relation of enzyme activities with enviromental factors. 1) We have found that the positional, optical and geometrical component ratio of hydroperoxides formed by the stereoselective oxygenation to linoleic acid, the ester and linoleylalcohol varied by these using substances. For the evidence we have proposed that in the enzymic oxygenation, it depend on the affinity with enzyme active site and functional group of substrates. 2) A possible mechanism of cleavage reaction of 13-hydroperoxides catalyzed by hydroperoxide lyase in tea chloroplasts was proposed to be an acid-catalyzed mechanism involved a nucleophilic substitution of water molecule. 3) When tea leaves were homogenized and incubated, the volatile C_6-compounds were formed much more by summer leaves than by winter leaves of tea plants. The enzyme lipolytic acyl hydrolase, lipoxygenase, fatty acid hydroperoxide lyase and alcohol dehydrogenase were responsible for the sequential reactions of C_6-compound formation from linoleic and linolenic acids in tea leaf lipides, and there were seasonal changes in their activities.
天然有機化合物討論会の論文
1985-09-07

58 青葉アルコールの生合成(その4) : 緑葉中の"green香"生成機構とその周辺

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