Characterization, biosynthesis, and release of neuropeptides from the x-organ-sinus gland system of the crab, Cardisoma carnifex

Separation of neuropeptides by high-pressure liquid chromatography and proteins by gel electrophoresis has been undertaken for the X-organ-sinus gland (XOSG) neurosecretory system of the crab, Cardisoma carnifex. Biosynthetic incorporation of [³H]leucine by isolated XOSG systems confirms synthesis of the peptides and certain of the proteins, as well as their calcium-dependent release during secretion evoked by elevation of saline potassium. Eleven peptides (mol wt < 7,000) are consistently found in significant quantities. Characterization of these shows them to represent three groups: 1) red-pigment concentrating hormone (previously sequenced, Fernlund and Josefsson, 1972); 2) 3 hyperglycemic peptides with amino acid compositions similar to those previously reported (Keller, 1981); and 3) 7 novel peptides whose biological activities have not been determined, labelled b, C, D, E, F, H, and I. Peptides b, C, D, E, F, and I can be explained by the partial proteolysis of peptide H at two internal sites, with non-proteolytic covalent modification of at least one of the amino-terminal fragments. Analysis of single glands shows different relative amounts of the b-I peptides in different animals, but with precise duplication of relative amounts of the b-I peptides in contralateral sinus glands. The data suggest that mixtures of peptides secreted may vary under physiological control and raise the question whether the physiological effects of such mixtures differ.