Enzymes - Biochemistry - Lecture Slides, Slides of Biochemistry

Download Enzymes - Biochemistry - Lecture Slides and more Slides Biochemistry in PDF only on Docsity! Enzymes (If you don’t have the energy, we can help!) Docsity.com Enzymes • Biological catalysts • Made primarily from proteins • Bind to substrate • Not used up • Speed up reaction Docsity.com Sources of Activation energy • Binding energy – Solvent released from active site when substrate binds increases ΔSsurr • Induced fit – Enzyme forces substrate into unstable transition state – Catalytic antibodies • Binding substrate brings reactive groups together Docsity.com Catalysis by an enzyme • E + S > ES > EP > E + P Docsity.com Enzyme Example Serine Proteases – Note side chain interactions – Substrate diffuses into active site Docsity.com Serine proteases • Half of protein diffuses out • Enzyme used up – Has to be regenerated Docsity.com Serine proteases • Water diffuses into active site • Juxtaposes chemical groups – Similar reaction to first Docsity.com Serine proteases ¢ New unstable intermediate generated Gey) a Tetrahedral intermediate Docsity.com Kinetics • Study of reaction rates • Why? – Used to determine mechanisms • Michaelis Menton kinetics V = rate of reaction • Vmax = maximum reaction rate [S] • Substrate concentration • Km = substrate concentration where rate is half maximal Docsity.com Michaelis-Menton Plot v, vs [S] Plot = NR = Qo V, (umal/min) o MF 8B ®@ @ Docsity.com Enzyme inhibition, Competitive • Both substrate and inhibitor bind to active site – Compete • Inhibitor blocks substrate from binding E S I E I S Docsity.com Noncompetitive Inhibition S I • Inhibitor binds to an allosteric site on the enzyme • Changes active site so substrate doesn’t bind I Docsity.com Michaelis- Menton Plot for noncompetitive inhibition uninhib Vmax/2 Km Vmax uninhib Vmax inhib V [S] Docsity.com Michaelis- Menton Plot for noncompetitive inhibition • Inhibition lowers Vmax • Km unchanged – Since inhibitor doesn’t bind to active site, changing amount of substrate will have no effect Docsity.com