立体化学
查尔酮合酶
查尔酮
查尔酮异构酶
异构酶
柚皮素
活动站点
生物合成
酶
化学
生物
生物化学
类黄酮
抗氧化剂
作者
Joseph M. Jez,Marianne E. Bowman,Richard A. Dixon,Joseph P. Noel
摘要
Chalcone isomerase (CHI) catalyzes the intramolecular cyclization of chalcone synthesized by chalcone synthase (CHS) into (2S)-naringenin, an essential compound in the biosynthesis of anthocyanin pigments, inducers of Rhizobium nodulation genes, and antimicrobial phytoalexins. The 1.85 A resolution crystal structure of alfalfa CHI in complex with (2S)-naringenin reveals a novel open-faced beta-sandwich fold. Currently, proteins with homologous primary sequences are found only in higher plants. The topology of the active site cleft defines the stereochemistry of the cyclization reaction. The structure and mutational analysis suggest a mechanism in which shape complementarity of the binding cleft locks the substrate into a constrained conformation that allows the reaction to proceed with a second-order rate constant approaching the diffusion controlled limit. This structure raises questions about the evolutionary history of this structurally unique plant enzyme.
科研通智能强力驱动
Strongly Powered by AbleSci AI