So we ultimately transform the alcohol group into a keto group that contains this carbonyl group shown here. So this molecule is known as the three keto, acyl coenzyme A. So the third step is the second oxidation step in which the hydroxyl group on the third carbon, the beta carbon, is transformed into the keto group in the process that produces a nicotine amine adenine dinucleotide molecule. Now, the enzyme that basically catalyzed this step is the l three hydroxy acyl coenzyme A dehydronase. And it only acts on the substrate molecule if it's the l isomer. And that's why this step is so important.