Which enzyme is responsible for destroying vitamin B1 (thiamine) and thereby associated with the deficiency disease beriberi?

Introduction:
Beriberi is a deficiency disease caused by lack of vitamin B1 (thiamine). Some foods and microorganisms contain enzymes that degrade thiamine, reducing bioavailability. This question tests recognition of the enzyme that cleaves thiamine and is therefore implicated in thiamine deficiency under certain dietary conditions.

Given Data / Assumptions:

• Target vitamin: thiamine (vitamin B1).
• Clinical outcome: deficiency symptoms of beriberi with prolonged inadequate intake or degradation.
• Candidate enzymes: oxidases and hydrolases with different substrates.

Concept / Approach:
Thiaminase catalyzes the cleavage of thiamine, rendering it inactive. Certain raw fish, ferns, and microbial contaminants may contain thiaminase. Cooking or processing usually reduces activity, but high intake of raw thiaminase-positive foods or contamination can contribute to deficiency when dietary thiamine is marginal.

Step-by-Step Solution:
Step 1: Map deficiency (beriberi) to the vitamin involved: thiamine.Step 2: Identify enzyme that specifically breaks thiamine: thiaminase.Step 3: Exclude enzymes acting on unrelated substrates (fatty acids or phenolics).Step 4: Conclude thiaminase is responsible.

Verification / Alternative check:
Nutritional biochemistry sources document thiaminase I and II forms capable of degrading thiamine, lowering its bioavailability and linking to deficiency in susceptible diets.

Why Other Options Are Wrong:

• Ascorbic acid oxidase: Acts on vitamin C, not thiamine.
• Lipoxygenase: Oxidizes polyunsaturated fatty acids; unrelated to thiamine.
• None of these: Incorrect because thiaminase fits the condition.
• Tyrosinase: Acts on phenols; not involved in thiamine degradation.

Common Pitfalls:
Confusing enzymes that impact other nutrients (e.g., vitamin C oxidase) with those directly degrading thiamine; overlooking processing effects that inactivate thiaminase.

Final Answer:
Thiaminase