Aconitate isomerase (EC 5.3.3.7) interconverts cis- and trans-isomers of aconitic acid. Expression of the gene encoding this enzyme was studied in maize (Zea mays L.) leaves depending on light regime. Aconitate isomerase was induced by white and by red light indicating the involvement of phytochrome in the regulation of gene expression. The enzyme was partially purified from maize leaves. The value of Km was 0.75 mM with cis-aconitate and 0.92 mM with trans-aconitate, pH optimum was 8.0-8.2 with both substrates, citrate and malate suppressed its activity. It is concluded that aconitate isomerase actively participates in the interconversion of cis- and trans-aconitate in the light providing a possibility of using the pool of trans-aconitate for the regulation of the tricarboxylic acid cycle activity and mediating citrate/isocitrate supply for the biosynthetic and signaling purposes in photosynthetic cells.

中文翻译：

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玉米叶中的乌头酸异构酶：光依赖性表达和动力学特性

乌头酸异构酶 (EC 5.3.3.7) 将乌头酸的顺式和反式异构体相互转化。根据光照条件在玉米 (Zea mays L.) 叶子中研究了编码该酶的基因的表达。白光和红光诱导附子酸异构酶，表明光敏色素参与基因表达的调节。该酶从玉米叶中部分纯化。顺式乌头酸的 Km 值为 0.75 mM，反式乌头酸的 Km 值为 0.92 mM，最适 pH 值为 8.0-8.2，两种底物柠檬酸盐和苹果酸抑制其活性。