Characterization, Biosynthesis, and Release of Neuropeptides from the X–Organ–Sinus Gland System of the Crab,Cardisoma carnifex

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Abstract
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.

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