Enzyme Lecture - Lecture 3

Holoenzyme Apoenzyme (Protein part) Non-protein part Tightly bound (Prothetic group) Loosely bound Cofactor Coenzyme ▪These are group of enzymes which are attached together and catalyze a certain reaction ▪They affect the substrate in sequential manner so that the product of the first enzyme will be...

Holoenzyme Apoenzyme (Protein part) Non-protein part Tightly bound (Prothetic group) Loosely bound Cofactor Coenzyme ▪These are group of enzymes which are attached together and catalyze a certain reaction ▪They affect the substrate in sequential manner so that the product of the first enzyme will be the substrate of the second one until formation of the final product. e.g. Pyruvate dehydrogenase complex. Enzymes in clinical diagnosis 1- Enzymes may be measured in cells to detect enzyme deficiency in certain diseases e.g. deficiency of red cell G6PD in favism. 2- Measuring the level of certain enzymes in blood plasma helps the diagnosis of many diseases e.g.: high levels of CK (CK-MB), LDH and aspartate aminotransferase (AST) are specific for myocardial infarction. Plasma enzymes may be functional, which are enzymes that perform a certain function in the blood, or nonfunctional. These are a group of enzymes which are characterized by the following: ▪ They catalyze the same reaction. ▪ They have different polypeptide chains which are produced by different genes. ▪ They are separated by electrophoresis (have different migration rate). ▪ They have different affinity to the substrate. ▪ They are usually affected in different ways by the different activators and inhibitors. ▪ They are present in the same or different cells. Creatine Kinase Creatine Kinase (CK) or Creatine Phosphokinase (CPK): *CK BB (in brain) *CK MB (in heart) *CKMM (in muscle) Clinical significance of enzymes 1- Biochemical reactions 2- Diagnosis of diseases Extracted and purified enzymes Medical applications Enzymes are used in detergents and washing soaps Industrial applications Amylase, lactases, cellulases are enzymes used to break complex sugars Pectinase act on hard pectin in fruit juice manufacture