羧基和咪唑基团在柚柠檬苦素类化合物糖基转移酶催化反应中的作用(英文)

作     者：M.R.KARIM F.HASHINAGA 

作者机构：Department of Biochemical Science and TechnologyFaculty of AgricultureKagoshima University 

出 版 物：《催化学报》 (Cuihua Xuebao Chin. J. Catalysis)

年 卷 期：2010年第31卷第12期

页      面：1445-1451页

核心收录：

学科分类：081705[工学-工业催化] 08[工学] 0817[工学-化学工程与技术] 

基　　金：Supported by Ministry of Education Culture Sports Science and Technology of Japan 

主　　题：chemical modification catalytic residue carboxyl group imidazole group uridine diphosphate glucosyltransferase pummelo albedo 

摘      要：Limonoid bitterness is a serious problem in the citrus industry worldwide. Limonoid glucosyltransferase is an enzyme that catalyzes the conversion of bitter limonoid into non-bitter limonoid glucoside while retaining the health benefit of limonoids in the juice. The immobilization of this enzyme in a column can solve the juice bitterness problem. More information about the catalytic residues of the enzyme is needed in this immobilization process. Glutamate/aspartate,histidine,lysine,tryptophan,serine,and cysteine residues were chemi-cally modified to investigate their roles in the catalytic function of limonoid glucosyltransferase. Inactivation of the enzyme following modi-fication of carboxyl and imidazole moieties was a consequence of a loss in substrate binding and catalysis in the glucosyltransfer reaction. The modification of a single histidine residue completely destroyed the ability of limonoid glucosyltransferase to transfer the D-glucopyranosyl unit. Tryptophan seemed to have some role in maintaining the active conformation of the catalytic site. Lysine also seemed to have some direct or indirect role in this catalysis but the modification of serine and cysteine did not have any effect on catalysis. Therefore,we conclude that the carboxyl and imidazole groups containing amino acids are responsible for the catalytic action of the enzyme.