Abstract
To investigate the mechanism on the melanin formation of the larval marking in the silkworm, the comparative studies on the tyrosinase activities in the cuticle and epidermis separated from the integuments of plain (p) and Striped (ps) have been done. The tyrosinase activity in the cuticle in both strains was higher than that of epidermis at all stages other than the moulting period, and Striped showed higher tyrosinase activity than plain in the cuticle, but the difference of tyrosinase activity in the epidermis between Striped and plain was not so obvious as in the cuticle. On the contrary, during the moulting period, the increase of the tyrosinase activity in the epidermis of Striped was higher than that of plain.
To find out the cause of such difference of tyrosinase activity between Striped and plain, the effect of M.I.A. counteracting the sulfhydryl group on the tyrosinase activity in the integuments of the silkworm larvae has been tested by expressing the degree of the visible change in color and the oxygen uptake by Warburg's manometer. From the result by the former method it seems that the addition of M.I.A. to the extract accerelate the darkening of the extract of the integument of plain as well as in the Striped, and yet the degree of accerelation in the former is higher than that in the latter. However, the effect of M.I.A. is not recognized in the investigation using Warburg's manometric method.
