Medical Enzymology By Amr S. Moustafa, M.D.; Ph.D. Assistant Prof. & Consultant, Medical Biochemistry Dept. College of Medicine, KSU

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Medical Enzymology By Amr S. Moustafa, M.D.; Ph.D. Assistant Prof. & Consultant, Medical Biochemistry Dept. College of Medicine, KSU

Michaelis-Menten Equation  E + S ES E + P  v ° = K m : Michaelis constant = (k-1 + k2) / k1 k1 K-1 k2 V max [S] K m + [S]

Michaelis-Menten Kinetics

Zero and First Order Reactions

Lineweaver-Burk Plot = + 1 v°v° KmKm V max [S] 1 V max

Inhibition of Enzyme Activity  Inhibitor: The velocity of the reaction  Reversible or irreversible  Competitive or noncompetitive

Competitive Inhibition -1  Inhibitors: Structural similarity to S Bind to S-binding site (compete with S) ES or EI complexes [S] overcomes the inhibition  K m But, no effect on V max

Competitive Inhibition -2

 Statin Drugs, e.g., Simvastatin (Zocor) Competitive Inhibition -3

Noncompetitive Inhibition -1  Inhibitors: No structural similarity to S Bind to different (allosteric) site ES or EI or ESI complexes [S] cannot overcome the inhibition  V max But, no effect on K m

Noncompetitive Inhibition -2

Noncompetitive Inhibition -3

Noncompetitive Inhibition -4  Lead and Ferrochelatase  Insecticides and actylcholinesterase  Covalent and irreversible

Therapeutic Potential of Enzyme Inhibition  β-Lactam antibiotics, e.g., Penicillin  Angiotensin-converting enzyme (ACE) inhibitors, e.g., Captopril  Statin drugs as antihyperlipidemic