This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Fluoride inhibit enzyme of which ion? 
Select and explain. 
A. Mg, B. Ca, C. Na, D. K
A: Mg
Answer: A: Mg 
Explanation: Enolase is a dimeric metal-activated metallo-enzyme, which uses two magnesium ions per subunit: the strongly bound conformational ion and the catalytic ion that binds to the enzyme-substrate complex inducing catalysis.