When we conduct our protein assay. So to demonstrate how we can measure enzyme activity, let's actually focus on a specific type of enzyme found ourselves known as lactate dehydrogenase. So lactate dehydrogenase is a biological catalyst that basically converts lactate into Pyruvate. In the process, we reduce NAD plus into NADH. So this is the oxidized version of nicotine amide adenine dinucleotide. And this is the reduced version of nicotine amy adenine dinucleotide.