So essentially, we can break down the first phase into four steps, and let's begin with reaction one. Step one. So in the first step, the enzyme that catalyzed the first step is known as glucosex phosphate dehydrogenase. Why? Well, because the substrate molecule is a glucose phosphate and this is actually a dehydrogenase reaction. So what happens is we have this NADP plus molecule that will act as an electron acceptor.