Catalase cofactor question: the essential non-protein metal associated with the enzyme catalase is:

Introduction / Context:
Catalase protects cells by rapidly decomposing hydrogen peroxide into water and oxygen. Its catalytic power depends on a specific metal cofactor embedded within a heme group. Identifying this metal is a common biochemistry recall item.

Given Data / Assumptions:

• We are discussing catalase (not peroxidase variants with different metals).
• Catalase contains a heme prosthetic group.
• The question asks for the non-protein metal at the active center.

Concept / Approach:
Catalase is a heme-containing enzyme, and the heme iron cycles between oxidation states during catalysis of 2 H2O2 → 2 H2O + O2. The iron participates directly in electron transfer and formation of high-valent intermediates (e.g., Compound I), enabling the rapid disproportionation of hydrogen peroxide.

Step-by-Step Solution:

Verification / Alternative check:
Spectral properties (Soret band) and EPR/Mössbauer studies confirm heme iron as the catalytic metal in typical catalases.

Why Other Options Are Wrong:
Magnesium/Zinc: Common in many enzymes but not the heme catalytic center of catalase. Manganese: Some catalase-peroxidases involve heme iron; manganese catalases exist in certain organisms but the canonical catalase referenced in basic courses is heme iron-based; the best single correct answer here is iron.

Common Pitfalls:
Confusing different peroxidative enzymes; remember “heme” points to iron as the central metal.

Final Answer:
iron