So this is a mixed function oxygenase. And what that means is it uses a diatomic oxygen. It takes one of the oxygen atoms within this diatomic molecule, places it on this, reactant the phenylalanine, and this basically forms the tyrosine. And this oxygen is shown here. Now, the other oxygen atom goes to form water, and that's exactly why water is released here. So phenylalanine hydroxylase is a mixed function oxygenase.