Schüz R, Heller W, Hahlbrock K
J Biol Chem. 1983 Jun 10;258(11):6730-4.
The substrate specificity of chalcone synthase, the key enzyme of flavonoid biosynthesis, was investigated. A purified enzyme preparation from cell suspension cultures of parsley (Petroselinum hortense) catalyzed chain elongations with acetate units from malonyl-CoA, using various aromatic and aliphatic CoA esters as starter molecules. Malonyl-CoA could not be replaced by malonyl acyl carrier protein in the standard chalcone synthase assay. Butyryl-CoA, hexanoyl-CoA, and benzoyl-CoA served as substrates for the condensation reaction with similar efficiency as 4-coumaroyl-CoA, the natural substrate of the enzyme. Acetyl-CoA and octanoyl-CoA were relatively poor substrates. Among the products formed with the two most efficient aliphatic substrates tested, butyryl-CoA and hexanoyl-CoA, were the respective chalcone analogues, phlorobutyrophenone and phlorocaprophenone. The possibility is discussed that chalcone synthase and the corresponding enzyme of fatty acid synthesis in higher plants, beta-ketoacyl-acyl carrier protein synthase, have a common evolutionary origin.
对黄酮类生物合成的关键酶查尔酮合酶的底物特异性进行了研究。从欧芹（Petroselinum hortense）细胞悬浮培养物中纯化得到的酶制剂，以各种芳香族和脂肪族辅酶A酯作为起始分子，催化丙二酰辅酶A的乙酸酯单元进行链延伸反应。在标准的查尔酮合酶测定中，丙二酰辅酶A不能被丙二酰酰基载体蛋白替代。丁酰辅酶A、己酰辅酶A和苯甲酰辅酶A作为缩合反应的底物，其效率与该酶的天然底物4-香豆酰辅酶A相似。乙酰辅酶A和辛酰辅酶A是相对较差的底物。在用两种最有效的脂肪族底物丁酰辅酶A和己酰辅酶A形成的产物中，分别是查尔酮类似物，即邻苯丁酰苯乙酮和邻苯己酰苯乙酮。文中讨论了高等植物中查尔酮合酶与脂肪酸合成的相应酶β-酮酰-酰基载体蛋白合酶具有共同进化起源的可能性。
