CHARACTERIZATION OF INSULIN-RECEPTOR FROM THE MUSCLE OF THE SHRIMP PENAEUS-JAPONICUS (CRUSTACEA, DECAPODA)

The beta-subunit of the insulin receptor from the muscle of the shrimp Penaeus japonicus exists as multiple subtypes with M(r) of 79,000, 77 ,000 and 75,000. Only the subunit of M(r) 79,000 is autophosphorylated after the addition of insulin. The autophosphorylation occurred speci fically at Tyr residues, as demonstrated by the specific subsequent de phosphorylation by the phosphotyrosyl protein phosphatase from the hum an placenta. The detergent, Triton X-100, and the metal ion, Mn2+, cau sed a noticeable enhancement of the autophosphorylation of shrimp insu lin receptors from the muscle. Okadaic acid activated the kinase activ ity of the insulin-stimulated insulin receptor, but not the basal acti vity of the insulin receptor without the addition of insulin. Futher s tudies comparing the insulin binding of the shrimp insulin receptor in the regulation of kinase activity of the multiple beta-subunit subtyp es from the shrimp muscle are under way.