The hemoregulatory peptide N-acetyl-Ser-Asp-Lys-Pro is a natural and specific substrate of the N-terminal active site of human angiotensin-converting enzyme.
Angiotensin I-converting enzyme (ACE) is a zinc-dipeptidyl carboxypeptidase, which contains two similar domains, each possessing a functional active site. Respective involvement of each active site in the degradation of the circulating peptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), a negative regulator of hematopoietic stem cell proliferation, was studied by using wild-type recombinant ACE and two full-length mutants containing a single functional site. Both the N- and C-active sites of ACE exhibit dipeptidyl activity toward AcSDKP, with Km values of 31 and 39 microM, respectively. However, the N-active site hydrolyzes the peptide 50 times faster compared with the C-active site, with kcat/Km values of 0.5 and 0.01 microM-1.s-1, respectively. The predominant role of the N-active site in AcSDKP hydrolysis was confirmed by the inhibition of hydrolysis using a monoclonal antibody specifically directed against the N-active site. The N-domain specificity for AcSDKP will aid the identification of specific inhibitors for this domain. This is the first report of a highly specific substrate for the N-active site of ACE, with kinetic constants in the range of physiological substrates, suggesting that ACE might be involved via its N-terminal active site in the in vivo regulation of the local concentration of this hemoregulatory peptide.
Rousseau
A
A
Centre National de la Recherche Scientifique, Institut de Chimie des Substances Naturelles, Gif-Yvette, France.
Michaud
A
A
Chauvet
M T
MT
Lenfant
M
M
Corvol
P
P
D000595:Amino Acid Sequence; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002455:Cell Division / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D006224:Cricetinae; D004789:Enzyme Activation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism* / Q000494:pharmacology; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D013379:Substrate Specificity
D000806:Angiotensin-Converting Enzyme Inhibitors; D002712:Chlorides; D009842:Oligopeptides; D007703:Peptidyl-Dipeptidase A; C058504:goralatide