This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
Co-factor for phosphofructokinase is 
Select and explain. 
A. Mg +2, B. Mn +2, C. Fe +2, D. Zn
A: Mg +2
Answer: A: Mg +2 
Explanation: Many of the glycolytic enzymes are sensitive to Mg2+. The most impoant effect is due to MgATP2-being a cofactor for a number of these enzymes while other chelation forms are inactive or inhibitory. The means by which Mg2+ and Mg2+ chelates of adenine nucleotides regulate the most impoant glycolytic enzymes--hexokinase, phosphofructokinase, aldolase, phosphoglycerate kinase, and pyruvate kinaseRef: DM Vasudevan, 7th edition