Lesson 7. REGULATION OF ENZYME ACTIVITY. CLASSIFICATION AND NOMENCLATURE OF ENZYMES. ISOZYMES. MEDICAL ENZYMOLOGY

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Task

Guidelines for performing the task

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Study

the effect of inhibitors on enzyme activity

1. Describe the classification of inhibitors.

2. Write down examples of inhibitors and explain the mechanism of their inhibitory effect.

3. Make a schematic representation of the mechanism of action for competitive inhibitors and noncompetitive inhibitors

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4. Draw the Lineweaver-Burk plots for competitive and noncompetitive inhibition. How do kinetic parameters of the enzyme (K_m, V_max) change under the effect of competitive and noncompetitive inhibitors?

5. Define the term allosteric center. What is the distinctive feature of allosteric enzyme kinetics?

6. Give examples of medical application of inhibitors

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Study the influence

of activators on enzyme activity

1. List the main types of activators of enzymes.

2. Study the mechanisms of action of inorganic ions as activators.

3. Activation by partial proteolysis. Which enzymes can be activated by partial proteolysis? What is the biological significance of this way of enzyme activation?

4. Study the mechanism of allosteric activation of enzymes.

5. Give examples of enzymes that are activated by association and dissociation of subunits and covalent modification (phosphorylation-dephosphorylation)

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Study isozymes and mul-tienzyme complexes

1. Give definitions of the term isozymes.

2. Give examples of enzymes that have isozymes. What is the biological significance of isozymes?

3. Describe the structure of isozymes of lactate dehydrogenase (LDH), creatine kinase (CK), alkaline phosphatase, and characterize each of them.

4. What is diagnostic and prognostic importance of determining the blood isozyme spectrum?

5. Define the term multienzyme complex. Give examples of such complexes

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Study the methods

of measuring enzyme activity

1. What is the basis for quantitative analysis of enzyme activity?

2. Which methods can be used for monitoring the conversion of the substrate to products in reactions catalyzed by salivary amylase and blood serum phos-phatase?

3. What does absolute activity, specific activity, and turnover number mean?

4. In what conditions the rate of enzyme catalyzed reaction is proportional to the concentration of enzyme?

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Study areas of medical enzymology

1. What is enzymopathology? Give examples of diseases caused by genetic defects of enzymes.

2. What is enzyme diagnosis? Write down examples of enzymes used in diagnostics of diseases (see the table below). What does tissue specificity of enzymes mean?

3. What is enszyme therapy? Give examples of enzymes used as medicines

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Study

immobilized enzymes

1. Define the term immobilized enzyme.

2. What are the advantages of using immobilized enzymes in practice?

3. Write the ways of enzyme immobilizing and materials used for this purpose.

4. Give examples of immobilized enzymes used in medicine

Enzyme

Disease that is accompanied by high enzymatic activity

Alanine aminotransferase Aspartate aminotransferase α-amylase

Lactate dehydrogenase (LDH)

Creatine kinase

y-glutamyltranspeptidase Pancreatic lipase Acidic phosphatase Alkaline phosphatase (isoenzymes) Glutamate dehydrogenase Sorbitol dehydrogenase

Hepatitis, myocardial infarction

Myocardial infarction, hepatitis, kidney diseases

Acute pancreatitis, parotitis

Myocardial infarction (LDH_1,2 isozymes), hepatitis

(LDH_4,5 isozymes), skeletal muscle injury (LDH_4,5 isoen-

zymes)

Myocardial infarction (MB isozyme), skeletal muscle lesion (MM isozyme), stroke (BB isozyme) Hepatitis, cirrhosis, alcoholic liver damage Acute pancreatitis, cancer of the pancreas Сarcinoma of prostate

Bone diseases, hepatitis, cholelithiasis and other diseases accompanied by cholestasis Acute hepatitis Acute hepatitis

Content of test tube

Test tube #

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1% solution of NaCl

1% solution of CuSO₄

Distilled water

Diluted saliva

1% solution of starch

Iodine test

Conclusions: