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The conversion of glucose to glucose-6-phosphate is the first reaction of glycolysis. This reaction requires hexokinase,...

The conversion of glucose to glucose-6-phosphate is the first reaction of glycolysis. This reaction requires hexokinase, Mg2+ ions as enzyme and cofactor, and ATP as substrate. What is the significance of Mg2+ ions in this reaction?

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Answer #1

Mg2+ involved in shielding the negative charges from the phosphate groups on the ATP molecule

In hexokinase, the phosphorus of the third phosphate of an ATP molecule reacts with the hydroxyl oxygen at C6 of glucose. The hydroxyl oxygen has a lot of negative charge on it and the phosphates of ATP do as well. Without Mg2+ cation, the oxygen could not get close enough to the phosphorus to react because it will be repelled by the negative charge on the phosphate groups.

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