AIIMS CRE, SNO-2024: Suicidal enzyme complexes often contain:

AIIMS CRE, SNO-2024

Biochemistry & Nutrition

Easy

Appeared in: AIIMS CRE, SNO-2024

Explanation

Cyclooxygenase (COX) is a well-documented 'suicide enzyme' that undergoes self-catalyzed destruction as part of its normal function.
During the conversion of arachidonic acid to prostaglandins, reactive intermediates are formed which irreversibly damage the enzyme's active site.
This process is also known as mechanism-based inactivation, where the enzyme participates in its own permanent deactivation.

Option A: Amylase is a hydrolase enzyme involved in digestion. It breaks down starch into sugars and functions repeatedly without being destroyed in the process.
Option C: Catalase is an antioxidant enzyme with one of the highest turnover rates known. It efficiently neutralizes hydrogen peroxide into water and oxygen and is not a suicide enzyme.
Option D: Lactase is a digestive enzyme found in the small intestine that breaks down lactose. Its deficiency leads to lactose intolerance, but its mechanism does not involve suicide inactivation.

Visual 1: Diagram: The cyclooxygenase (COX) pathway, illustrating the conversion of arachidonic acid to prostaglandins and highlighting the step where self-inactivation occurs.
Visual 2: Infographic: A comparison of a standard enzyme reaction versus a suicide inhibition mechanism, showing how the inhibitor product binds irreversibly to the enzyme.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Enzyme kinetics and suicide inhibition as background academic context rather than a clinical decision trigger.
Understanding suicide inhibition is fundamental in pharmacology, as many drugs, such as aspirin, allopurinol, and penicillin, function as suicide inhibitors.
Aspirin's irreversible inhibition of COX in platelets is the basis for its long-lasting antiplatelet effect, crucial for preventing heart attacks and strokes. Since platelets lack a nucleus, they cannot produce new enzymes, so the effect lasts for the platelet's lifespan (7-10 days).
What if? If a patient takes a reversible COX inhibitor like ibuprofen shortly before taking aspirin, the ibuprofen can occupy the active site, blocking aspirin from binding. This reduces aspirin's irreversible, cardioprotective effect, demonstrating a clinically significant drug-drug interaction.

How to Approach the Question

First, define the key term in the question: 'Suicidal enzyme'. This is an enzyme that is irreversibly inactivated as a consequence of its own catalytic mechanism.
Next, review the general function of each enzyme listed in the options.
Amylase and Lactase are digestive enzymes. Catalase is a protective antioxidant enzyme. Cyclooxygenase is involved in inflammation and prostaglandin synthesis.
Recall or deduce which of these functions involves a self-destructive process. The synthesis of prostaglandins by COX is known to generate reactive species that inactivate the enzyme.
Therefore, connect the definition of a suicidal enzyme to the known mechanism of Cyclooxygenase to identify it as the correct answer.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana 7th Edition — Part 2 (pp 421-820 of 840) p. 346-454