Hexokinase is found in the first step of glycolysis. Responsible for the transfer of a phosphoryl group from ATP to various hexoses, it (as do all kinases) requires a divalent metal ion such as Mg2+ or Mn2+. It is inhibited by glucose 6-phosphate and activated by insulin. The reaction of hexokinase in glycolysis is the phosphorylation of glucose to glucose 6-phosphate. The conditions for this reaction are as follows: standard conditions: -4.0 kcal/mol physiological conditions: -8.0 kcal/mol this is an irreversible step