title: Differences in the hydrolysis of enkephalin congeners by the two domains of angiotensin converting enzyme.
abstract: The hydrolysis of enkephalin (Enk) congeners by the isolated N- (N-ACE) and C-domain of angiotensin I converting enzyme (ACE) and by the two-domain somatic ACE was investigated. Both Leu5- and Met5-Enk were cleaved faster by the C-domain than by N-ACE; rates with somatic ACE were 1600 and 2500 nmol/min/nmol enzyme with both active sites being involved. Substitution of Gly2 by D-Ala2 reduced the rate to 1/3rd to 1/7th of that of the Enks. N-ACE cleaved Met5-Enk-Arg6-Phe7 faster than the C-domain, probably with the highest turnover number of any naturally occurring ACE substrate (7600 min(-1)). This heptapeptide is also hydrolyzed in the absence of Cl-, but the activation by Cl- is unique; Cl- enhances the hydrolysis of the heptapeptide by N-ACE but inhibits it by the C-domain, yielding about a 5-fold difference in the turnover number at physiological pH. This difference may result in the predominant role of the N-domain in converting Met5-Enk-Arg6-Phe7 to Enk in vivo.
authors.affiliation: University of Illinois College of Medicine at Chicago, Department of Pharmacology, 60612, U.S.A.
authors.forename: P A
authors.initials: PA
authors.lastname: Deddish
authors.forename: H L
authors.initials: HL
authors.lastname: Jackman
authors.forename: R A
authors.initials: RA
authors.lastname: Skidgel
authors.forename: E G
authors.initials: EG
authors.lastname: Erdös
mesh_terms: D000701:Analgesics, Opioid / Q000378:metabolism; D001665:Binding Sites; D002712:Chlorides / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004743:Enkephalin, Leucine / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*
chemical_list: D000701:Analgesics, Opioid; D002712:Chlorides; D004745:Enkephalins; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C013801:enkephalin-Met, Ala(2)-; D016308:Enkephalin, Leucine-2-Alanine; C027511:enkephalin-Met, Arg(6)-Phe(7)-; D007703:Peptidyl-Dipeptidase A