In the process, we release a carbon dioxide and we generate the much needed reducing agent molecules, the NADPH molecule. So the first phase of the pencil phosphate pathway is the oxidative breakdown of glucose to release carbon dioxide and generate NADPH molecules. So let's see exactly how this takes place. 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.