Isolation and characterization of sinus gland neuropeptides with both mandibular organ inhibiting and hyperglycemic effects from the spider crab Libinia emarginata

Using two-step reverse phase HPLC, we isolated and purified three peptides with mandibular organ inhibiting hormone (MO-IH) activity from the spider crab Libinia emarginata. One of the peptides, P22, gave a yield of 355 ng/SG. The others gave lower yields: P21, 9 ng/SG; P25, 67.5 ng/SG. The molecular weight was determined to be 8,439 for P25, 8,474 for P22, and 8,398 for P21 by mass spectrometry. All three peptides have similar amino acid compositions and contain 72-76 residues. We believe these peptides to be different isoforms of one family. The MO is more sensitive to the two minor isoforms, P21 and P25. All three isoforms can inhibit MO activity to a maximum inhibition of 70%. All three isoforms gave a significant hyperglycemic effect when injected into de-eyestalked fiddler crabs Uca pugilator. We believe the MO-IHs to be members of the crustacean hyperglycemic hormone (CHH) family, having similar amino acid compositions and both biological activities. (C) 1996 Wiley-Liss, Inc.