Purification and amino acid composition of the hyperglycemic neurohormone from the sinus gland ofOrconectes limosus and comparison with the hormone fromCarcinus maenas

Summary

The hyperglycemic neuropeptide was purified to homogeneity from sinus glands of the crayfish,Orconectes limosus, by a simple two-step procedure consisting of preparative polyacrylamide gel electrophoresis followed by gel chromatography on Sephadex G-50. A total of 40 μg was obtained from 1,670 lyophilized sinus glands. The molecule consists of 58 amino acid residues plus an undetermined number of Trp residues. The following amino acid composition was found: Asx₈; Thr₂; Ser₃; Glx₆; Pro₁; Gly₂; Ala₃; 1/2 Cys₄; Val₅; Met₁; Ile₃; Leu₅; Tyr₅; Phe₃; Trp_n.d.; His₀; Lys₃; Arg₄. A minimal MW of 6,812 was calculated. The N-terminal residue appears to be blocked. Analysis of the pure hormone on an isoelectric focusing gel gave an pI of 5.04–5.10. The hormone differs from that ofCarcinus (Keller and Wunderer, 1978) in its amino acid composition and pI (Carcinus: 4.55–4.63). The following features are common for both theOrconectes and theCarcinus hormone: the size of the molecule, the blocked N-terminus, the presence of two intrachain disulfide bridges and the general acidic nature. A dose ofOrconectes hormone which is highly effective in this species has no or only very little effect inUca, whereas the same dose ofCarcinus hormone, which is markedly hyperglycemic in the brachyuranUca, exhibits no effect in the astacuranOrconectes. In animals of 10 g live weight, injection of 1.9 pmol/animal causes a threefold increase in the hemolymph glucose level.