Biochemistry 1000 Enzymes I SOME TERMS Catalysts Ribozymes Substrate Active site II CLASSIFICATION A Naming ex pyruvate decarboxylase B 6 Main Classes 1 Oxidoreductase 2 Transferases 3 Hydrolyases 4 Lyases 5 Isomerases 6 Ligases III Many Enzymes require cofactors for activity Cofactors o coenzymes o metals Holoenzyme Apoenzyme IV WHAT DO THEY DO Review of rxn thermodynamics Activation E Free energy G change in free energy G Enzymes do not alter the G of a reaction o G is negative o G is positive o At equilibrium G 0 o G of a reaction depends o The G of a reaction The free energy change is given by Bring in the enzyme Decrease activation energy Transition state V BINDING MODELS A Lock Key Model B Induced Fit Model Active Site Binding energy VI CATALYSIS A acid base catalysis B covalent catalysis C metal ion catalysis D Catalysis by approximation and orientation VII EXAMPLE THROUGHOUT CHAPTER protease chymotrypsin VIII Enzyme Kinetics A ka kd B TYPICAL EXPERIMENT o velocity o initial velocity vo ii Mathematical equation to describe hyperbolic curve above Michaelis Menton equation iii MM equation works at all points on the curve 1 low S Km S therefore S omitted in denominator o Hyperbolic shape C MATHEMATICAL ANALYSIS i Michaelis Menton proposal vo Vmax S Km S Vmax Km vo Vmax S Km 2 high S Km S vo Vmax S Vmax S 3 Also when Km S vo Vmax S Vmax 2 S 2 D LINEWEAVER BURK PLOTS double reciprocal equation D OTHER KINETIC PARAMETERS A kcat B Specificity constant IX ENZYME REGULATION 3 Types of enzyme regulation A Allosteric inhibition o feedback inhibition B Covalent modification of enzymes C Protoleytic Other Regulation Mechanisms 1 Change amt of enz 2 Change cellular location of enz 3 Change pH 4 Attach modifying grps phosphate 5 Temperature enhances the rate of enzyme catalyzed reactions X Enzyme Inhibition Inhibitor I TWO TYPES OF INHIBITION Irreversible Reversible A Irreversible B Reversible Several Types of reversible inhibitors 1 competitive Lineweaver Burk plot 2 Uncompetitive inhibitors Lineweaver burk plot 3 mixed Lineweaver Burk plot Special case for Mixed Non competitive inhibition Lineweaver Burk plot