L7 Enzymes -II: Mechanism of Action PDF

L7 Enzymes -II Mechanism of Action Dr. Salah Omar December 11, 2024 www.gmu.ac.ae College of Health Learning Objectives: Define active site of an enzyme List the four properties of the active site that determine...

L7 Enzymes -II Mechanism of Action Dr. Salah Omar December 11, 2024 www.gmu.ac.ae College of Health Learning Objectives: Define active site of an enzyme List the four properties of the active site that determine substrate specificity; Outline the mechanism of action of enzymes Explain factors that affect enzyme activity Describe inhibition of enzymes and types of inhibition Define isoenzymes and explain their clinical uses Enzymes Lower a Reaction’s Activation Energy Formation of Products from Substrate (bound to enzyme), followed by release of the products 2) The active site of the enzyme Enzymes bind substrates to their active site and stabilize the transition state of the reaction. The active site of the enzyme is the place where the substrate binds and at which catalysis occurs. The active site binds the substrate, forming an enzyme-substrate(ES) complex. Binding site Active site Catalytic site Enzymatic reaction steps 1. Substrate approaches active site 2. Enzyme-substrate complex forms 3. Substrate transformed into products 4. Products released 5. Enzyme recycled 1. Effect of temperature on enzyme activity  2. Effect of pH on enzyme activity The pH optimum varies for different enzymes. Most enzyme: neutral pH (6-8).  Isoenzymes (Isozymes) The multiple forms of an enzyme catalyzing the same general reaction but differing in physical & chemical properties. Usually come from different tissues Very useful in the diagnosis of diseases Methods commonly used for separation of isoenzymes: a. Electrophoresis b. ELISA c. Heat Denaturation d. Use of Inhibitors  Inhibitors.Inhibitors are chemicals that reduce the rate of enzymatic reactions..The are usually specific and they work at low concentrations..They block the enzyme but they do not usually destroy it..Many drugs and poisons are inhibitors of enzymes in the nervous system.  The effect of enzyme inhibition Irreversible inhibitors: Combine with the functional groups of the amino acids in the active site, irreversibly. Reversible inhibitors: These can be washed out of the solution of enzyme by dialysis.  Applications of inhibitors Negative feedback: end point or end product inhibition Poisons: snake bite, plant alkaloids and nerve gases. Medicine antibiotics: sulphonamides, sedatives and stimulants. December 11, 2024 www.gmu.ac.ae College of Health  Enzymes in clinical diagnosis An enzyme test is a blood test or urine test that measures levels of certain enzymes to assess how well the body’s systems are functioning and whether there has been any tissue damage. (why?)  Common enzymes used for clinical diagnosis include: alanine aminotransferase(ALT,also called glutamate pyruvate transaminase,GPT) alkaline phosphatase amylase aspartate aminotransferase creatine kinase lactate dehydrogenase Plasma Enzyme Patterns can be used in diagnosis of Different Diseases a. Example: Acute myocardial infarction b.Acute viral hepatitis