生物化学教学课件：Enzymes

Enzymes1Whathaveyouheardaboutenzymes?2ThinkaboutyourbreakfastIfeaten,digestedinhours;Ifnoteaten,stayforyears…..34Orotatedecarboxylaseknon

=2.8

10-16

s-178

106yearkcat=39s-125

10-3secondkcat/knon

=1.4

1017Enzymesarebiologicalcatalysts.Enzymesaffectreactionrates,notequilibria.5Whyshouldwestudyenzymes?6Enzyme-inhibitorexamplesLipase（脂肪酶）inhibitor(抑制剂);Acetylcholinesterase（乙酰胆碱酯酶）inhibitor.Anti-AIDScock-tailtherapy（疗法;7①

Indiancurare②Organophosphorus③AD-treating

medicineacetylcholineacetylcholinesterase①②③8Coagulationcascade9Howdoenzymeswork?10VNQHLCGSHLVEALYLVCGERGVNQHLCGSHLVEALYLVCGERGchymotrypsin….NH-CH-COOHCH2-C6H4-OHNH2-CH-CO-….CH2-CH-(CH3)2Substrate底物Product产物Chymotrypsin胰凝乳蛋白酶11Chymotrypsin胰凝乳蛋白酶(PDB7GCH)12Chymotrypsin胰凝乳蛋白酶Activesite活性位点13Catalytictriad:Ser195,His57,Asp102.Inhibitor抑制剂Chymotrypsin胰凝乳蛋白酶141516Mechanismofchymotrypsin(.tw/BCbasics/Animation1.htm)

17Shouldenzymesbestfittheirsubstrates?Howdoenzymescatalyzechemicalreactions?1819No.ClassTypeofreactioncatalyzed1OxidoreductaseTransferofelectrons2TransferaseGrouptransferreaction3HydrolaseHydrolysisreaction4LyaseAdditionofgroupstodoublebonds,orformationofdoublebondsbyremovalofgroups5IsomeraseTransferofgroupswithinmoleculestoyieldisomericforms6LigaseBondformationcoupledwithATPhydrolysisInternationalclassificationofenzymesSerineendopeptidase:ChymotrypsinTrypsinSubtilisin……ECECEC220APFirstorderreactionZeroorderreactionSecondorderreactionA+BP21AP22APWhen[A]=[A]0,v=V0When[A]=[A]/2,t=t1/2Radioactiveisotopedecomposition:Slope=V0V0:initialvelocity(initialrate).t1/2:half-life