Significance of a carboxyl-terminal amide moiety in the folding and biological activity of crustacean hyperglycemic hormone.

Recombinant peptides related to Pej-SGP-I, one of several crustacean hyperglycemic hormones (CHHs) existing in the kuruma prawn Penaeus japonicus, were expressed in bacterial cells, and then purified after being allowed to refold. Their circular dichroism spectra suggested that the recombinant Pej-SGP-I having a free carboxyl-terminus (rPej-SGP-I-OH) differed slightly in secondary structure from the recombinant Pej-SGP-I having an amidated C-terminus (rPej-SGP-I-amide). The hyperglycemic activity of rPej-SGP-I-amide was comparable to that of natural Pej-SGP-I, whereas rPej-SGP-I-OH showed weaker hyperglycemic activity by approximately one order of magnitude. These results indicate that the C-terminal amide of CHH affects secondary structure and is significant in conferring hyperglycemic activity.