Enzyme 2 Lecture Notes - International University of Africa

International University of Africa Faculty of Medicine Department of Biochemistry Biochemistry – 1 Enzymes-2 By Dr. Mohammed Abdelrheem 5/10/2024 1  Enzymes Classification  Enzymes are divided into six major classes...

International University of Africa Faculty of Medicine Department of Biochemistry Biochemistry – 1 Enzymes-2 By Dr. Mohammed Abdelrheem 5/10/2024 1  Enzymes Classification  Enzymes are divided into six major classes:  Oxidoreductases: involved in oxidation reduction reactions (e.g. dehydrogenases and oxidases)  Transferases: transfer functional groups (e.g. amino or phosphate group) between donors and acceptors (e.g. aminotransferase and kinases) 5/10/2024 2  Hydrolases: transfer water to catalyse the hydrolysis of substrates (e.g. proteases and phosphatases)  Lyases: add or remove the elements of water, ammonia or carbon dioxide to (or from) double bonds (e.g. decarboxylases, and synthases)  Isomerase: catalyze changes within one molecule (e.g. mutases)  Ligases: join two molecules together at the expense of ATP (e.g. synthetases and carboxylases) 5/10/2024 3 5/10/2024 4 Factors affecting enzymes activity: 1. Substrate concentration 2. Enzyme concentration 3. pH 4.Temperature How enzyme activity measured ? Decrease in substrate concentration Increase in product concentration  Reaction velocity is the amount of substrate converted in to product per time Increase in substrate concentration leads to increase in the velocity of reaction. At Vmax increase in the amount of substrate causes no increase in the velocity of the reaction  Km is the substrate concentration at half maximum velocity It measures the enzyme affinity to substrate Low Km reflects a high affinity High Km reflect a low affinity 5/10/2024 9 Increase in the enzyme concentration leads to increase in the velocity of reaction Effect of pH :  Optimal pH : the pH at which enzyme acts maximally. Above or below this pH the rate of reaction will decreased. Each enzyme has its own pH. Effect of temperature :  Temperature: the rate of enzyme-catalyzed reaction increases with increasing temperature up to optimum point, then it decrease because enzymes are thermolabile. Most enzymes are denatured at 55-60. 5/10/2024 14  THANKS 5/10/2024 15