Abstract
Abstract The effects of various chemical and enzymatic treatments on the biological activity of porcine luteinizing hormone-releasing hormone (LH-RH), which were performed before the elucidation of the structure of this hormone, are described. LH-RH activity was abolished by the following endopeptidases: chymotrypsin, subtilisin, papain, and thermolysin, but not by pepsin or trypsin. Exopeptidases did not affect LH-RH activity, but a purified preparation of pyrolidone carboxylpeptidase did. Treatment with various chemical reagents showed that tyrosine, histidine, tryptophan, and arginine in LH-RH are important for its biological activity. Nitrous acid and Edman degradation did not inactivate LH-RH. The results are in agreement with the determined structure of LH-RH. This hormone also showed a high follicle-stimulating hormone-releasing hormone activity. The inactivation of LH-RH was always accompanied by a loss of follicle-stimulating hormone-releasing hormone activity. These experiments also shed some light on the structure-activity relationship of this hormone.
Highlights
In the early stages of structural work on this hormonal polypeptide, we investigated the effects of various enzymes and chemical reagents on the luteinizing hormone-releasing hormone (LH-RH)/FSH-releasing hormone (FSH-RH)
The lack of inactivation by several exopeptidases and by Edman degradation was in good agreement with these findings (Table I)
Since no Iysine is present in the molecule, the result of nitrous acid treatment is understandable
Summary
The effects of various chemical and enzymatic treatments on the biological activity of porcine luteinizing hormone-releasing hormone (LH-RH), which were performed before the elucidation of the structure of this hormone, are described. The results are in agreement with the determined structure of LH-RH This hormone showed a high follicle-stimulating hormone-releasing hormone activity. Porcine LH-RH was clearly demonstrated to induce the release of LH in sheep [11] and in humans [12] We purified this hormone from 160,000 pig hypothalami, proved it to be a polypeptide [13, 14], and showed its amino acid sequence to be (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-. Because of the sensitivity of the assay systems employed, only very small amounts of pure material were required for this type of experiment and much suggestive information was obtained Some of this information proved to be useful for planning sequential analysis, and provided strong supports for the structure proposed by us. Some experiments on the effect of such treatments on FSH-RH activity (l&19) have been reported
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