Arginase activity in the silkworm,Bombyx mori: developmental profiles, tissue distribution and physiological role

Abstract

Arginase activity was studied in the silk-worm,Bombyx mori. 1. The specific activity remained low from the larval to mid-pupal stage in both sexes. In males, it then increased markedly in the late-pupal stage, reached a maximum in young adults, and then gradually decreased with age, whereas in females it remained almost constant throughout development and ageing (Fig. 1). 2. Of all organs of both sexes, the vesicula seminalis of adult males had the highest arginase activity, the activity in this organ amounting to 95% of the total activity in adult males. The specific arginase activity in this organ was at least 50 times those in other organs. The enzyme activity in the vesicula seminalis increased very greatly during metamorphosis to adults (Tables 1, 2, 3). 3. When the vesicula seminalis was incubated withl-[14C(U)]-ornithine, large amounts of radio-activity were found in the metabolites proline and glutamate, suggesting the conversion of ornithine, produced by arginase, to proline (Fig. 2, Table 4). 4. Proline and succinate were effective substrates for the respiration of silkworm spermatozoa, whereas glucose, α-glycerophosphate and pyruvate were not used.