So remember, we have two substrate molecules. This is one of them in this step, and this is the second one in this step. So we have the keto substrate molecule, and in this particular case, the keto substrate that we're going to look at is the CETO heptulose seven phosphate. So in the first step, we basically have the formation of that shift base. And once these two react, we basically form this molecule. In the process, we actually kick off a water molecule.