Which ion acts as an activator of alkaline phosphatase?

• A. Magnesium
• B. Calcium
• C. Zinc
• D. Iron

Answer: (A)

Magnesium acts as a key activator for alkaline phosphatase because this enzyme is a metalloenzyme that requires divalent metal ions to function. The presence of Mg2+ helps stabilize the enzyme-substrate complex and supports the catalytic process of phosphate release. While zinc is also involved in the enzyme’s active site and participates directly in catalysis, the ion most commonly described as activating alkaline phosphatase in practical terms is magnesium. Calcium can interact with the enzyme but does not reliably serve as the activator, and iron has no role in activating this enzyme.