Purification and amino acid sequence of the ovulation neurohormone of Lymnaea stagnalis.

The neurosecretory caudodorsal cells of the freshwater pulmonate snail Lymnaea stagnalis produce an ovulation hormone [caudodorsal cell hormone (CDCH)] that is stored and released at the periphery of the intercerebral commissure. In the present study, CDCH has been purified and sequenced by micromethods. CDCH has been isolated, starting with a hydrochloric acid extract of commissures, by chromatofocusing, by high-performance, gel-permeation chromatography, and by reversed-phase, high-performance liquid chromatography. This procedure resulted in a 1690-fold purification and a 66% recovery. The data of the sequence analysis of CDCH are in agreement with the amino acid composition and reveal the following sequence of 36 amino acids: H-Leu-Ser-Ile-Thr-Asn-Asp-Leu-Arg-Ala-Ile-Ala-Asp-Ser-Tyr-Leu-Tyr-Asp-Gln-His -Trp-Leu-Arg-Glu-Arg-Gln-Glu-Glu-Asn-Leu-Arg-Arg-Arg-Phe-Leu-Glu-Leu-OH. Enzyme data indicate that the COOH end of the hormone is amidated. CDCH has a calculated isoelectric point of 9.0 and a calculated M(r) of 4529. CDCH shares a 44% homology with the sequence of the egg-laying hormone of the marine opisthobranch mollusc Aplysia californica.