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

General Objectives  Regulation of metabolic reactions  Control of metabolic pathways  Medical Therapeutic

Specific Objectives  Nature and structure of enzymes  Nomenclature and IUBMB classes  Properties of enzymes  Factors affecting enzyme activity  Enzyme Kinetics  Enzyme inhibitors &medical applications

Enzymes: Nature and Function  Protein catalysts  Exception: Ribozymes RNA with catalytic activity  Substrate (S) Product (P) Enzyme (E)  ES complex

Enzymes: Structure-1  Active site: 3-D Surface complementary to S

Enzymes: Structure-2  Holoenzyme: Protein + Nonprotein Protein : Apoenzyme (inactive) Nonprotein: Cofactor Co-enzyme Prosthetic group

Enzymes: Properties  Catalytic efficiency: Turnover number (k cat ): No. S molecules into P/E molecule/Sec  Specificity: Highly specific: One or few S One type of reaction

Subcellular Localization of Enzymes

Factors affecting Enzymatic activity  Substrate concentration [S]  Temperature  The pH  Note: Reaction velocity(v ° ): No. S molecules into P/time e.g., μmol/minute

Factors affecting Enzymatic activity 1. Substrate Concentration

Factors affecting Enzymatic activity 2. Temperature

Factors affecting Enzymatic activity 3. The pH