Abstract
In nitric oxide (NO)-generating cells, the citrulline/NO cycle is an important pathway in controlling the arginine supply because NO is generated from arginine by the activation of NO synthase. Argininosuccinate synthetase (AS ; EC 6.3.4.5) is a rate-limiting enzyme in the citrulline/NO cycle, which catalyses the condensation of citrulline and aspartate to form argininosuccinate, the immediate precursor of arginine. In this report, we examined AS activity in the parotid glands of rat, rabbit, mouse, and guinea pig. AS activity was detected in all species, and, in the rabbit parotid gland, most of the activity was observed in the cytosolic fraction. In the parotid glands of postnatal rabbits, AS activity increased prior to NOS activity. These results suggest that AS contributes to NO generation in the parotid gland.
