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: Biochemistry
Metal needed for function of enolase is: 
Select and explain. 
A. Magnesisum, B. Calcium, C. Copper, D. Iron
A: Magnesisum
Answer: A: Magnesisum 
Explanation: Enolase is inhibited by fluoride, and when blood samples are taken for measurement of glucose, it is collected in tubes containing fluoride to inhibit glycolysis. The enzyme is also dependent on the presence of either Mg2+ or Mn2+. The phosphate of phosphoenolpyruvate is transferred to ADP by pyruvate kinase to form two molecules of ATP per molecule of glucose oxidized. Ref: Harper 28th edition, chapter 17.