So what is a hexokinase? Well, a hexokinase is a protein kinase that basically catalyzes the addition of asphalt groups onto hexosugars. And glucose is an example of a HEXO sugar. It contains these six carbon atoms. Now, like all protein kinases, hexokinase requires a diveant metal atom to actually function effectively. And that's because the divalent metal atom such as magnesium two plus or magnesium two plus, interacts with the ATP molecules.