Biochemistry Lecture 11 PDF

Biochemistry Biomedical significance of Enzymes LECTURE (11) DR. El-Sawy 1  Biochemistry B...

Biochemistry Biomedical significance of Enzymes LECTURE (11) DR. El-Sawy 1  Biochemistry Biomedical significance of Enzymes  Different molecular forms of enzyme that have same catalytic activity, but they are physically distinct.  Differ in : Electrophoretic mobility (migration in an electric field). Def : Liability to inhibitors. 1. True genetic variants (True isoenzyme) Produced by more than one gene. Each gene produces one subunit. Sources 2. Muliple forms -post-translational modification Produced by the same gene but the subunits undergo different post-translation modifications in different organs. 1. Lactate dehydrogenase (LDH). 2. Creatine kinase (CK). Examples 3. Acid phosphatase. 4. Alkaline phosphatase. DR. El-Sawy 2  Biochemistry Biomedical significance of Enzymes Lactate dehydrogenase (LDH) Creatine kinase (CK)  Tetramer formed of 4 protein subunits. Def  Dimmer formed of 2 protein subunits.  Each subunit is called protomer.  H (heart).  B (brain). Types  M (muscle).  M (muscle). Isoenzyme Formed of Increases in Isoenzyme Increases in Myocardial infarction Brain tumors Myocardial infarction Heart diseases Isoenzymes Leukemia Skeletal muscle diseases Viral hepatitis Viral hepatitis Isoenzymes are not only important for diagnosis but also indicate the diseased organ. Functions  Clinically important to differentiate ( ) heart, liver & blood  Clinically important to differentiate ( ) brain, heart & skeletal ms diseases. diseases. DR. El-Sawy 3  Biochemistry Biomedical significance of Enzymes  Isoenzymes are not only important for diagnosis but also indicate the diseased organ.  Lactate dehydrogenase enzyme (LDH) increases in: Isoenzyme Increases in Myocardial infarction (heart disease) Leukemia (blood disease) Viral hepatitis (liver disease)  Creatine kinase enzyme (CK) increases in: Isoenzyme Increases in Brain tumors Myocardial infarction (heart disease) Skeletal muscle diseases (muscle dystrophy) DR. El-Sawy 4  Biochemistry Biomedical significance of Enzymes Classification : Non-functional plasma Functional plasma enzymes enzymes  Present in plasma in higher  Present in plasma in very Plasma concentration in comparison low concentration in Concentration to tissues. comparison to tissues. Functions  Have known functions.  No known functions. Substrate  Always present in blood.  Absent from blood.  Liver , heart, brain & Site of  Liver synthesis skeletal muscles  Different enzymes ↑ in Effect of  Decrease in liver disease. disease different organ diseases. 1. Clotting factors: 1. ALT, AST, CK, LDH, Prothrombin 2. Alkaline phosphatase. Examples 2. Lipoprotein lipase 3. Acid phosphatase 3. Pseudo-choline esterase 4. Amylase 1. Obstruction of pathway. 2. ↑ Permeability of cell membrane: tissue hypoxia. 3. Cell damage with release Sources of its contents of enzymes into blood. DR. El-Sawy 5  Biochemistry Biomedical significance of Enzymes Medical importance of non-functional plasma enzymes : Enzyme Disease Heart diseases Lactate dehydrogenase Blood diseases. Liver diseases Heart diseases Creatine kinase Brain diseases Skeletal muscle diseases. Serum glutamic pyruvic transaminase Liver diseases. (SGPT) = Alanine transaminase (ALT) Serum glutamic oxalacetic Liver diseases transaminase (SGOT) = Aspartate Heart diseases. transaminase (AST) Obstructive liver disease. Alkaline phosphatase Bone disease. Acid phosphatase Prostate cancer. Amylase Pancreatitis. lipase DR. El-Sawy 6