title: Novel natural peptide substrates for endopeptidase 24.15, neurolysin, and angiotensin-converting enzyme.
abstract: Endopeptidase 24.15 (EC; ep24.15), neurolysin (EC; ep24.16), and angiotensin-converting enzyme (EC; ACE) are metallopeptidases involved in neuropeptide metabolism in vertebrates. Using catalytically inactive forms of ep24.15 and ep24.16, we have identified new peptide substrates for these enzymes. The enzymatic activity of ep24.15 and ep24.16 was inactivated by site-directed mutagenesis of amino acid residues within their conserved HEXXH motifs, without disturbing their secondary structure or peptide binding ability, as shown by circular dichroism and binding assays. Fifteen of the peptides isolated were sequenced by electrospray ionization tandem mass spectrometry and shared homology with fragments of intracellular proteins such as hemoglobin. Three of these peptides (PVNFKFLSH, VVYPWTQRY, and LVVYPWTQRY) were synthesized and shown to interact with ep24.15, ep24.16, and ACE, with K(i) values ranging from 1.86 to 27.76 microm. The hemoglobin alpha-chain fragment PVNFKFLSH, which we have named hemopressin, produced dose-dependent hypotension in anesthetized rats, starting at 0.001 microg/kg. The hypotensive effect of the peptide was potentiated by enalapril only at the lowest peptide dose. These results suggest a role for hemopressin as a vasoactive substance in vivo. The identification of these putative intracellular substrates for ep24.15 and ep24.16 is an important step toward the elucidation of the role of these enzymes within cells.
authors.affiliation: Department of Histology and Embryology, Cell Biology Program, Institute of Biomedical Sciences, University of São Paulo, Brazil.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Rioli
authors.forename: Fabio C
authors.initials: FC
authors.lastname: Gozzo
authors.forename: Andrea S
authors.initials: AS
authors.lastname: Heimann
authors.forename: Alessandra
authors.initials: A
authors.lastname: Linardi
authors.forename: José E
authors.initials: JE
authors.lastname: Krieger
authors.forename: Cláudio S
authors.initials: CS
authors.lastname: Shida
authors.forename: Paulo C
authors.initials: PC
authors.lastname: Almeida
authors.forename: Stephen
authors.initials: S
authors.lastname: Hyslop
authors.forename: Marcos N
authors.initials: MN
authors.lastname: Eberlin
authors.forename: Emer S
authors.initials: ES
authors.lastname: Ferro
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D008297:Male; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D013552:Swine
chemical_list: D006454:Hemoglobins; D010446:Peptide Fragments; C473218:hemopressin; D007703:Peptidyl-Dipeptidase A; D008666:Metalloendopeptidases; C022510:thimet oligopeptidase; C062316:neurolysin