And the enzyme that catalyzes process is known as d three hydroxybutyrate dehydrogenase. And that's because it produces D three hydroxybutyrate, the third and final ketone body inside our body. So we have acetoacitate, one ketone body, a second ketone body, the third ketone body. This is not metabolizable, but acetoacitate. And D three hydroxybuty can be broken down by ourselves to form energy molecules, as we'll see in just a moment. Now, this process requires NADH because it's a reduction step.