Amino acid sequences and activities of multiple hyperglycemic hormones from the Kuruma prawn, Penaeus japonicus.

By means of a single-step reversed-phase HPLC, six CHH family peptides were isolated from sinus gland extracts of the kuruma prawn, Penaeus japonicus. Five of these peptides (Pej-SGP-I, -II, -III, -V, and -VI) expressed hyperglycemic activity and were considered to be the hyperglycemic hormones of this prawn. The amino acid sequences of the five peptides were determined (the amino acid sequence of Pej-SGP-III had been previously determined), revealing that all consisted of 72 amino acid residues with a free amino-terminus and an amidated carboxyl-terminus. They showed considerable sequence similarity to one another, but much less similarity to Pej-SGP-IV with molt-inhibiting activity, the sequence of which had also been determined previously. Examination of the dose-response relationship of these peptides showed that they were equally potent but had different efficacies, which were in the order of Pej-SGP-V, -VI > -III, -I > -II, corresponding well with their sequence characteristics.