So the first step, or actually the first three steps, are catalyzed by an enzyme known as carbomolphostate synthetase. Now, recall in the urea cycle, we also use a carbon phosphate synthetase enzyme, but that enzyme is type one and it lies in the mitochondria. This enzyme is type two and it's found in a cytoplasm. So this is actually not the same enzyme that we saw in the urea cycle. So what this enzyme does is it catalyzes three steps. And so it contains three different active sites.