And so we form this enzyme that does not contain the modified histidine, as well as a two, three BPG. Now, this two, three BPG is only present in very small amounts. Why? 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.