title: Isolation and characterization of a new bradykinin potentiating octapeptide from gamma-casein.
abstract: Peptides that display bradykinin-potentiating activity have been obtained from a number of distinct sources, such as snake venoms, fibrinogen, and casein. This paper describes the isolation and sequencing of a novel bradykinin-potentiating peptide, generated by tryptic hydrolysis of the gamma-casein chain. No homology was found to other known vasoactive or vasopotentiating peptides. The octapeptide Tyr-Pro-Val-Gln-Pro-Phe-Thr-Glu, corresponding to the gamma-casein(114-121) sequence, was isolated from the tryptic hydrolysis of gamma-casein and also synthesized by solid-phase peptide synthesis. Both natural and synthetic peptides had the same retention time in HPLC and displayed a selective potentiating activity on isolated guinea-pig ileum for bradykinin and Lys-bradykinin but were not able to potentiate the effects of Met-Lys-bradykinin, Ile-Ser-bradykinin, angiotensin II, acetylcholine, or histamine. Intravenous injections of bradykinin and of bradykinin-potentiating octapeptide produced a persistent hypotension in conscious rats, a pattern that was not obtained when the octapeptide was replaced by captopril. This bradykinin-potentiating octapeptide is a strong competitive inhibitor of endo-oligopeptidase A (EC 3.4.24.15, formerly EC 3.4.22.19), but it has low inhibitory potency towards angiotensin-converting enzyme (EC 3.4.15.1). Thus, our results suggest that other peptidases in addition to angiotensin-converting enzyme, such as endo-oligopeptidase A, may contribute to the reduction of the effective concentration of bradykinin in the circulation.
authors.affiliation: Biochemistry Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: I
authors.initials: I
authors.lastname: Lebrun
authors.forename: F L
authors.initials: FL
authors.lastname: Lebrun
authors.forename: O B
authors.initials: OB
authors.lastname: Henriques
authors.forename: A K
authors.initials: AK
authors.lastname: Carmona
authors.forename: L
authors.initials: L
authors.lastname: Juliano
authors.forename: A C
authors.initials: AC
authors.lastname: Camargo
mesh_terms: D000595:Amino Acid Sequence; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001920:Bradykinin / Q000502:physiology*; D002364:Caseins / Q000737:chemistry* / Q000494:pharmacology; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006168:Guinea Pigs; D006868:Hydrolysis; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000187:drug effects; D009842:Oligopeptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D011492:Protein Hydrolysates / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D014357:Trypsin; D014590:Uterine Contraction / Q000187:drug effects
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002364:Caseins; D009842:Oligopeptides; D011492:Protein Hydrolysates; C026375:trypticase-soy broth; D014357:Trypsin; D001920:Bradykinin