Progress in the study of the catalytic mechanism of pericyclic enzyme

Zhou Jiahai, State Key Laboratory of life organic chemistry, Shanghai Institute of organic chemistry, Chinese Academy of Sciences, and Tang Yi, UCLA, analyzed the crystal structure of high-resolution Lepi and its compound with substrate analogues or products 4, 5 and 6, and through the cooperation with Kendall of UCLA The research group of Houk carried out theoretical calculation and systematically explained the molecular mechanism of Lepi catalysis The work was published online July 22 in nature chemistry Cai Yujuan, doctoral student of zhoujiahai research group, Yang Hai, postdoctoral student of Tang Yi research group and Masao Ohashi are the first authors of the paper Cyclization is very important in the field of synthesis It can construct many carbon carbon / carbon heteroatom bonds at the same time, and often has high regioselectivity and stereoselectivity However, the discovery of new cycloenzymes and the analysis of their catalytic mechanism are of great significance to the development of the future cycloreactions However, in nature, there are few reports about the enzymes that catalyze the cycle reaction In 2017, Tang Yi's research group reported a S-adenosylmethionine (SAM) - dependent multifunctional cyclase Lepi, which can not only catalyze the heterodiels alder (HDA) reaction, but also the reverse Claisen rearrangement reaction (nature, 2017, DOI: 10.1038 / nature23882) Lepi belongs to the O-methyltransferase family, but it has no methyltransferase activity Why can the enzyme stereoselectively catalyze dehydration, HDA and reverse Claisen rearrangement? What is the role of Sam? In order to answer these questions, Zhou Jiahai research group, Tang Yi research group and Kendall Houk research group conducted in-depth research The parent structure of Lepi protein was analyzed by single wavelength scattering of selenium In this structure, the two Lepi molecules are intertwined with each other in N-terminal domain, while the C-terminal domain is a typical Rossman folding super secondary structure with O-methyltransferase family, and each Lepi molecule combines with a coenzyme Sam Combined with the structure of Lepi and 4, 5, 6 complexes, the calculation of transition state complex structure and biochemical experiments, this paper proposes that in the process of catalytic dehydration of Lepi, H133 as the hydroxyl group of pyridinone, r295 and the nearby hydrogen bond network promote the reaction In HDA reaction and reverse Claisen rearrangement reaction, Sam, H133 and r295 and other polar residues in the active pocket work together to produce a suitable electric field, which makes the reactants in the proper orientation for the reaction, stabilize the transition state, reduce the energy barrier, realize electrostatic catalysis and promote the reaction.