Inhibitor potencies and substrate preference for endothelin-converting enzyme-1 are dramatically affected by pH.
Phosphoramidon has been shown to inhibit endothelin-converting enzyme-1 (ECE-1) in a remarkably pH-dependent manner (Ahn et al. Arch Biochem Biophys 1998;359:258-68). In order to determine whether this dramatic pH-dependence is a general phenomenon of ECE-1, two structurally unrelated ECE-1 inhibitors, PD 069185 and CGS 31447, were tested for ECE-1 inhibition at various pH values. Our data indicate that the potencies of these ECE-1 inhibitors are also highly affected by pH. ECE-1 is known to have a very sharp activity optimum at neutral pH which is in marked contrast to the acidic pH optimum for ECE-2. However, our results show that the pH optimum for ECE-1 activity is highly substrate-dependent. ECE-1 hydrolyzes the small peptide hormones bradykinin and substance P with acidic pH optima of 5.6-5.8, which sharply contrasts the neutral pH optimum with big ET-1 as substrate. These data suggest that the substrate preference for ECE-1 is highly affected by pH and that this pH-dependence for substrate preference might be one way of controlling the specificity of the enzyme in vivo.
Fahnoe
D C
DC
Department of Biochemistry, Parke-Davis Pharmaceutical Research, Division of Warner Lambert Company, Ann Arbor, Michigan 48105, USA.
Knapp
J
J
Johnson
G D
GD
Ahn
K
K
D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors*; D001920:Bradykinin / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008666:Metalloendopeptidases; D063065:Organophosphonates / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology*; D013373:Substance P / Q000378:metabolism; D013379:Substrate Specificity; D013777:Tetrazoles / Q000494:pharmacology*
C113055:CGS 31447; D063065:Organophosphonates; C110777:PD 069185; D011480:Protease Inhibitors; D011799:Quinazolines; D013777:Tetrazoles; D013373:Substance P; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; C000606923:ECE1 protein, human; C000606924:ECE2 protein, human; D000072396:Endothelin-Converting Enzymes; D001920:Bradykinin