Case study- Enzyme Inhibition- A 54-year-old man complains of an acute onset of unilateral eye pain and reduction in the visual acuity….

Basic concept

Enzymes are catalysts of biological system. They speed up the rate of the reaction without themselves getting consumed during the process of catalysis. Active site is the place where the actual reaction between enzyme and substrate takes place. Coenzymes and cofactors are required by some of the enzymes to further accelerate the rate of enzyme catalyzed reaction. Many factors influence the rate of reaction including temperature, pH, substrate, enzyme and product concentration. Km denotes the affinity of the enzyme for its substrate, whereas Vmax signifies the maximum reaction velocity attained by enzyme catalyzed reaction.

The enzyme activity can be regulated by covalent or allosteric modification and enzyme concentration can be modified by induction, repression or degradation. Enzyme inhibitors are commercially used as drugs, poisons or research tools. Enzyme activity can be inhibited by competitive, non competitive, uncompetitive, allosteric or suicidal mechanisms. Enzymes can be used as therapeutic or diagnostic agents. Enzyme/ Isoenzyme estimations can signify the underlying tissue/organ damage or defects. Serial enzyme estimations can help predict the prognosis or response to drugs in patients with chronic illnesses.

Question of the day

A 54- year-old man complains of an acute onset of unilateral eye pain and reduction in the visual acuity. On physical examination, conjunctival injection (eye redness) and a mild-dilated and non reactive pupil is observed. Fundoscopic examination reveals cupping of the optic disc. Recognizing the signs and symptoms as glaucoma, the medication Acetazolamide is administered to decrease the production of aqueous fluid and lower the intraocular pressure. Acetazolamide is a non competitive inhibitor of carbonic anhydrase and therefore will cause:

A. An increase in Km

B. A decrease in Km

C. An increase in V max

D. A decrease in Vmax

E. A decrease in both Km and Vmax

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1 Response

  1. Ans D. decrease in Vmax

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