%0 Journal Article
%T PossibleRoleofCarboxylandImidazoleGroupsintheCatalysisofPummeloLimonoidGlucosyltransferase
%J ´ß»¯Ñ§±¨
%P 1445-1451
%D 2010
%X £¿Limonoidbitternessisaseriousprobleminthecitrusindustryworldwide.Limonoidglucosyltransferaseisanenzymethatcatalyzestheconversionofbitterlimonoidintonon-bitterlimonoidglucosidewhileretainingthehealthbenefitoflimonoidsinthejuice.Theimmobilizationofthisenzymeinacolumncansolvethejuicebitternessproblem.Moreinformationaboutthecatalyticresiduesoftheen-zymeisneededinthisimmobilizationprocess.Glutamate/aspartate,histidine,lysine,tryptophan,serine,andcysteineresidueswerechemi-callymodifiedtoinvestigatetheirrolesinthecatalyticfunctionoflimonoidglucosyltransferase.Inactivationoftheenzymefollowingmodi-ficationofcarboxylandimidazolemoietieswasaconsequenceofalossinsubstratebindingandcatalysisintheglucosyltransferreaction.ThemodificationofasinglehistidineresiduecompletelydestroyedtheabilityoflimonoidglucosyltransferasetotransfertheD-glucopyranosylunit.Tryptophanseemedtohavesomeroleinmaintainingtheactiveconformationofthecatalyticsite.Lysinealsoseemedtohavesomedirectorindirectroleinthiscatalysisbutthemodificationofserineandcysteinedidnothaveanyeffectoncatalysis.There-fore,weconcludethatthecarboxylandimidazolegroupscontainaminoacidsareresponsibleforthecatalyticactionoftheenzyme.
%K chemicalmodification
%K catalyticresidue
%K carboxylgroup
%K imidazolegroup
%K uridinediphosphateglucosyltransferase
%K pummeloalbedo
%U http://www.chxb.cn/CN/abstract/abstract20242.shtml