And to actually be able to catalyze this reaction, that histidine has to be modified with the addition of a phosphoryl group. And to see what we mean, let's take a look at these two steps. So in step one, we basically have this enzyme. And inside the active side of the enzyme, we have the histadine that has been modified by the addition of the phosphoryl group. And so in step one of this reaction, what happens is this three phosphorylycerate moves into the active side, and in step one, this molecule, the enzyme, transfers this phosphoryl group from the histidine of that enzyme onto the second position of this molecule. So essentially, we attach this phosphoryl group onto carbon number two, and we form the two three by or bisphosphoglycerate.