Boland M J, Wong E
Eur J Biochem. 1975 Jan 2;50(2):383-9. doi: 10.1111/j.1432-1033.1975.tb09814.x.
The chalcone-flavanone isomerase from soya bean seed has been purified 8300-fold. A molecular weight of 15,600 plus or minus 1000 has been determined for the enzyme. Effects of iodoacetamide and sodium tetrathionate on the enzyme, and pH dependence of the catalytic step, indicate that a sulphydryl group is not involved in the reaction mechanism and the catalytic group is probably an imidazole side chain in the basic form. The kinetics of the isomerisation of isoliquiritigenin to liquiritigenin have been examined and show that at pH 7.6 the reaction is reversible with an equilibrium constant of 37 in favour of flavanone. A number of flavonoid compounds competitively inhibit the reaction, suggesting a possible regulatory role for this enzyme in flavonoid biosynthesis.
大豆种子中的查尔酮-黄烷酮异构酶已被纯化了8300倍。已测定该酶的分子量为15,600±1000。碘乙酰胺和连四硫酸钠对该酶的影响以及催化步骤的pH依赖性表明，巯基不参与反应机制，催化基团可能是碱性形式的咪唑侧链。已研究了异甘草素异构化为甘草素的动力学，结果表明，在pH 7.6时，该反应是可逆的，平衡常数为37，有利于黄烷酮的生成。许多黄酮类化合物竞争性抑制该反应，表明该酶在黄酮类生物合成中可能具有调节作用。
