Muscle Enzymes
Clinically important muscle enzymes include creatine kinase and lactate dehydrogenase.
Creatine Kinase
Creatine kinase (CK) is most abundant in cells of brain, cardiac and skeletal. In addition to their abundance in above tissues, it also occurs in other tissues such as smooth muscle. In normal physiological condition the CK activity is 46- 171 U/L (for male) and 34-145 U/L (for female). Serum CK level elevates in all types of muscular dystrophy. Quite high values of CK are noted in viral myositis, polymyositis and similar muscle disease. Under the circumstances of neurogenic muscle disease such as: myasthenia gravis, multiple sclerosis and Parkinsonism, the level of serum CK is normal. CK consist of two protein subunits, M (for muscle) and B (for brain) and exist as three different isoforms namely BB (CK-1), MB (CK-2) and MM (CK-3). CK-MM is the predominant isoenzyme in skeletal and cardiac muscle and is detectable in the plasma of normal subjects. CK-BB is present in high concentrations in the brain and in the smooth muscle of the gastrointestinal and genital tracts.
Lactate Dehydrogenase
Lactate dehydrogenase (LD) catalyses the reversible interconversion of lactate and pyruvate. LD has a molecular weight of 134 kDa and is widely distributed in the body, with high concentrations in cells of cardiac and skeletal muscle, liver, kidney, brain and erythrocytes. Five isoforms (LD-1 to LD-5) of LD are existing. The normal physiological limit of LD is 180-360 U/L.
Other clinically important enzymes includes acid phosphatase, glucose -6- phosphate dehydrogenase, cystathionine a-synthase and sphingomyelinase.
Intext Quections
1. ……………… and ……………… are enzymes which involves in pancreatic destruction.
2. Molecular weights of amylases in human plasma ranges ……………… to ……………… kDa.
3. Plasma level of amylase activity fails to fall after an attack of ………………
4. Alkaline phosphatases, gamma-glutamyltransferase and glutamate dehydrogenase are markers of ………………
5. Clinically important muscle enzymes include ……………… and ………………
1. Enzymes are protein catalyst produced by a cell and responsible ‘for the high rate’ and specificity of one or more intracellular or extracellular biochemical reactions.
2. Enzymes posses the catalytic power to facilitates life processes in essentially all life-forms from viruses to man.
3. Enzymes are found in all tissues and fluids of the body.
4. Intracellular enzymes catalyze the reactions of metabolic pathways.
5. Plasma membrane enzymes regulate catalysis within cells in response to extracellular signals.
6. Enzymes are broadly classified into 6 major groups namely Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases and Ligases.
7. Enzymes may be simple proteins, or complex enzymes (presence of nonprotein part, called as prosthetic group).
8. Coenzymes functions as transporters of chemical groups from one reactant to another.
9. Activity of a particular enzyme may be affected by many external factors such as concentration of substrate, product, enzyme, hydrogen ion, temperature, activators and inhibitors.
10. Enzyme inhibitors plays a vital role in clinical utility and are useful as antibacterial, anti-malarial, anti-cancer molecule and treatment of metabolic disorders such as gout. Thus measurement of enzymes level in serum is applied in diagnostic application.
Terminal Questions
1. Define enzyme?
2. Write about classification of enzymes?
3. Give a brief discussion about various factors affecting enzyme activity?
4. What are metallo enzymes?
5. Define isozymes?
6. What are co-enzymes?
7. Differentiate synthase and synthatase?
8. Write a note on clinically important enzymes?
9. Describe in detail about the liver enzymes used in clinical diagnosis?
10. Give some examples of enzyme inhibitory drugs?
Answers To Intext Questions
1. Protein
2. Proteins
3. Water
4. Ammonium sulfate and Trichloroacetic acid
1. Six
2. Oxidoreductases
3. Metallo enzymes
4. Synthetases
5. Glycogen synthase and Alanine synthase
1. Co-enzymes
2. Protein and co-enzyme
3. Organic
4. Two
1. Enzyme concentration
2. Enzyme reaction
3. 9-10
4. Xanthine oxidase and gout
1. Isozymes
2. Gene
3. Lactate dehydrogenase
4. Bone
1. a-amylase and lipase
2. 54 to 62 kDa
3. Acute pancreatitis
4. Cholestasis
5. Creatine kinase and lactate dehydrogenase
