《食品生物化學》課件-6-1酶的概述

OverviewofenzymesFoodBiochemistry食品生物化學目錄CONTENTS1234TheconceptandmolecularcompositionofenzymeCharacteristicsofenzymeactionEnzymenomenclatureClassificationofenzymesTheconceptandmolecularcompositionofenzyme01Anoverviewofenzymes6.1TheconceptandchemicalnatureofenzymesEnzymesarebiocatalystsproducedbyactivecellswithhighcatalyticefficiencyandhighspecificity.Thevastmajorityofenzymesaremadeupofproteins,andafewaremadeupofnucleicacids(RNA),calledribozymes.FoodbiochemistryAnoverviewofenzymes6.1MolecularcompositionofenzymesAccordingtothecompositionofenzymescanbedividedintosimpleenzymesandbindingenzymes.Simpleenzymeshaveonlyproteins.Bindingenzymesincludeproteinparts(enzymeproteins)andnon-proteinparts,andthecombinationofthetwoiscalledholoenzyme,andonlytheholoenzymehascatalyticactivity.FoodbiochemistryCharacteristicsofenzymeaction02Anoverviewofenzymes6.1Comparedwithinorganiccatalysts,enzymeshavethefollowingcharacteristics:HighcatalyticperformanceHighlyspecificRegulationofenzymeactivityTheinstabilityofenzymeactivityFoodbiochemistryAnoverviewofenzymes6.1HighcatalyticperformanceThecatalyticefficiencyoftheenzymeis108-1020timeshigherthanthatofthenon-catalyticreaction,and107-1013timeshigherthanthatofthegeneralcatalyst.FoodbiochemistryAnoverviewofenzymes6.1HighlyspecificAnenzymeonlyactsonacompoundoraclassofcompounds,oracertainchemicalbond,catalyzesachemicalreactionoraclassofchemicalreactionsandproducescertainproducts,calledthespecificityorspecificityoftheenzyme.FoodbiochemistryAnoverviewofenzymes6.1AbsolutespecificityActsononlyonesubstratetoproduceaproductofaparticularstructure.RelativelyspecificCanactonaclassofcompoundsorachemicalbond.StereoisomerismspecificitySpecificrequirementsofenzymesforthestereoscopicconfigurationofsubstrates.FoodbiochemistryAnoverviewofenzymes6.1RegulationofenzymeactivityTherearetwomaintypesofregulationandcontrolofintracellularenzymes.Thefirsttypeistheregulationofenzymeconcentration.Thesecondcategoryistheregulationofenzymeactivity.FoodbiochemistryAnoverviewofenzymes6.1TheinstabilityofenzymeactivityEnzymesareextremelysensitivetoenvironmentalconditions,andgenerallyperformenzymaticreactionsundernormaltemperature,atmosphericpressure,andappropriatepHconditions.FoodbiochemistryEnzymenomenclature03Anoverviewofenzymes6.1CustomarynomenclatureNamedaccordingtothesubstrate;(2)namedaccordingtothetypeofreactioncatalyzed;(3)thefirsttwoprinciplesshallbenamedtogether;(4)Namedaccordingtothesourceorothercharacteristicsoftheenzyme.FoodbiochemistryAnoverviewofenzymes6.1SystematicnomenclatureThenameofeachenzymeshouldclearlyindicatethesubstrateoftheenzymeandthenatureofthecatalyticreaction,ifoneenzymecatalyzestwosubstrates,theyareseparatedby":".Forexample,thenameoftheenzymethatcatalyzesthefollowingreactionis"ATP:glucosephosphotransferase":ATP+D-glucose→ADP+D-glucose-6-phosphateFoodbiochemistryClassificationofenzymes04Anoverviewofenzymes6.101OxidoreductasesClassificationofenzymesFoodbiochemistryAnoverviewofenzymes6.10102OxidoreductasestransferasesClassificationofenzymesFoodbiochemistryAnoverviewofenzymes6.1010203hydrolasesClassificationofenzymesOxidoreductasestransferasesFoodbiochemistryAnoverviewofenzymes6.1Classificationofenzymes0102hydrolasesOxidoreductasestransferases04lyases03Foodbiochemistry0102hydrolasesOxidoreductasestransferases04lyases03Anoverviewofenzymes6.1Classificationofenzymes05isomerases