Arginine biosynthesis and metabolism in terrestrial snails

1. 1. Arginine synthesis was studied by the incorporation in vivo of [C¹⁴]-labeled precursors into protein arginine in Otala (= Helix) lactea, Helix aspersa and Bulimulus alternatus. The pattern of incorporation and the specific conversions obtained with these precursors were consistent with the pathway for arginine biosynthesis as it is known in other organisms. 2. 2. A comparison of the incorporation of [C¹⁴]bicarbonate into protein arginine, aspartate and glutamate indicated that the rate of arginine synthesis in vivo is significant in supplying arginine for protein synthesis. 3. 3. Arginine degradation in O. lactea and H. aspersa tissues was shown to be due to the combined action of arginase, urease and δ-ornithine transaminase. Because of the action in vivo of urease, there is a rapid turnover of urea in these two species. Urease is absent from B. alternatus hepatopancreas and the urea formed from arginine in this tissue accumulates.