Arginase activity in mollusks

[摘要] A survey of sixty-two mollusks was made for arginase activity, The enzyme was found to be present in all terrestrial forms examined, while the distribution in fresh water and marine mollusks was random. When arginase is present, the highest levels occur in the digestive gland or ;;liver;; of the mollusks. The ;;liver;; of Otala laetea, whose tissues were examined in more detail, was found to have a level of activity which was consistently higher than that of the other tissues by ten- to twenty-fold. In a series of forty-five individuals of Otala, the arginase levels varied by several orders of magnitude among individuals. This variation was not attributable to any readily apparent environ-mental factor. An investigation of the metabolism of (guanidino-14C)-DL- arginine, (5-14C)-DL-arginine, (2-14C)-DLornithine, and (14C)-urea in whole cell preparations of two land snails with widely differing levels of activity (Bulimulus alternatus and Otala lactea) was carried out. The temperature optima, heat stability, and cation activation characteristics of crude preparations of Otala and rat were compared. This comparison revealed the following: 1. Snail arginase attains a maximum activity at 35° whereas the temperature optimum of rat enzyme is 65°. 2. The arginase activity of the rat extracts Is dependent to a large extent on the presence of a bivalent ;;co-cation;;, whereas thnt of snail is not. 3. Rat, beef, and snail extracts were all found to be activated by Cd++ and Mn++ : no stimulation of activity could be elicited with Ni++ or Co++ in auy of the three species. 4. After partial purification of the rat and snail extracts, the behavior of the two preparations as regards dependence on Mn++ was identical with that of the crude systems.

[发布机构] Rice University