Well, because it then reacts with this same enzyme, histidine complex, in a slightly different reaction. So even though this reaction is possible, another reaction that can take place is the following. So, in step two, we have that same enzyme, histidine complex, and that same two, three BPG. Except now, instead of taking off that phosphoryl group from the second carbon, we take off that phosphoryl group from the third carbon. And so once we take off this phosphoryl group, this one here, we basically regenerate that enzyme histidine, with the modified group complex. And we also form the final product, the two phosphaglycerate.