Chemical and Pharmaceutical Bulletin
Online ISSN : 1347-5223
Print ISSN : 0009-2363
ISSN-L : 0009-2363
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Structure–Activity Relationships of Neuromedin U. V. Study on the Stability of Porcine Neuromedin U-8 at the C-Terminal Asparagine Amide under Mild Alkaline and Acidic Conditions
Takako KawaiAkira ShibataKatsuro KurosawaYuki SatoSachiko KatoKazuhiro OhkiTadashi HashimotoNaoki Sakura
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2006 Volume 54 Issue 5 Pages 659-664

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Abstract
Porcine neuromedin U-8 (X-Asn-NH2, X=H-Tyr-Phe-Leu-Phe-Arg-Pro-Arg) is occasionally unstable in the biological fluids used for bioassay as well as in the acidic solutions used for purification of synthetic peptides. In this study, HPLC examination of an incubate solution of X-Asn-NH2 revealed that the main decomposition products in Tyrode's solution (pH 7.4) were either α- or β-monocarboxylic acid analogs (X-Asn-OH or X-Asp-NH2), and that no dicarboxylic acid analog (X-Asp-OH) was produced. Further investigation, employing a model peptide (Y-Asn-NH2, Y=Benzoyl-Pro-Arg) incubated in a 0.1 M sodium bicarbonate solution at 60 °C, revealed that the decomposition of C-terminal Asn-NH2 occurred through the formation of an aminosuccinimide intermediate (Y-Asu), at a rate faster than that of Y-Asn-Ser peptide but slower than that of Y-Asn-Gly peptide. Mild acid hydrolysis of X-Asn-NH2 examined in a 1 M HCl solution at 60 °C yielded X-Asn-OH and X-Asp-NH2, which further decomposed to yield X-Asp-OH. The C-terminal degradation of X-Asn-NH2 resulted in reduced biological and immunochemical binding activities.
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© 2006 The Pharmaceutical Society of Japan
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