title: Measuring angiotensin-I converting enzyme inhibitory activity by micro plate assays: comparison using marine cryptides and tentative threshold determinations with captopril and losartan.
abstract: To determine the angiotensin-I converting enzyme (ACE) inhibitory activity of marine cryptides, different methods were tested. ACE inhibition was measured using two synthetic substrates, (N-[3-(2-furyl) acryloyl]-Phe-Gly-Gly (FAPGG) and N-hippuryl-His-Leu hydrate salt (HHL)), and a natural one, angiotensin-I. The IC50 value (defined as the concentration of inhibitory molecule needed to inhibit 50% of the ACE activity) of the reference synthetic inhibitor captopril was in the nanomolar range (1.79-15.1 nM) when synthetic substrates were used, whereas it exhibited IC50 of micromolar range (16.71 μM) with angiotensin-I. We chose losartan, an antagonist of angiotensin-II receptor as negative control for the ACE inhibition. Losartan was also able to inhibit ACE whatever the substrate tested, with IC50 of micromolar range (17.13-146 μM). We defined this value as a limit above which molecules are not showing in vitro ACE inhibitory activity. Val-Trp (VW), Val-Tyr (VY), Lys-Tyr (KY), Lys-Trp (KW), Ile-Tyr (IY), Ala-Pro (AP), Val-Ile-Tyr (VIY), Leu-Lys-Pro (LKP), Gly-Pro-Leu (GPL), Ala-Lys-Lys (AKK), and Val-Ala-Pro (VAP) were tested as inhibitors of ACE with synthetic and natural substrates. IC50 displayed were substrate-dependent. With FAPGG as substrate, IW, VAP, KY, IY, AP, AKK, and VIY show IC50 values over the IC50 value of losartan and should not be considered as inhibitors of ACE. VY, VW, KW, and LKP exhibited IC50 value lower than the IC50 value of losartan for all substrates tested and were thus considered as good candidates for effectively decreasing hypertension. It appears that the comparison of IC50 is not consistent when IC50 values are obtained with different substrates and different methods. In vitro ACE inhibitory activity assays should always include various ACE substrates and references such as captopril and a negative control to obtain data reliable to discriminate ACE inhibitory peptides.
authors.affiliation: Université de La Rochelle , Laboratoire LIENSs UMR CNRS-7266, Approches Moléculaires: Environnement Santé, site Marie Curie, UFR Sciences Technologies Santé , F-17042 La Rochelle, Cedex-1, France.
authors.forename: Yesmine
authors.initials: Y
authors.lastname: Ben Henda
authors.forename: Anis
authors.initials: A
authors.lastname: Labidi
authors.forename: Ingrid
authors.initials: I
authors.lastname: Arnaudin
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bridiau
authors.forename: Régis
authors.initials: R
authors.lastname: Delatouche
authors.forename: Thierry
authors.initials: T
authors.lastname: Maugard
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Piot
authors.forename: Frédéric
authors.initials: F
authors.lastname: Sannier
authors.forename: Valérie
authors.initials: V
authors.lastname: Thiéry
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Bordenave-Juchereau
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000032:analysis*; D002216:Captopril / Q000032:analysis*; D057075:Enzyme Assays / Q000295:instrumentation / Q000379:methods*; D019808:Losartan / Q000032:analysis*; D010446:Peptide Fragments / Q000032:analysis*; D007703:Peptidyl-Dipeptidase A / Q000032:analysis*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D010446:Peptide Fragments; D002216:Captopril; D007703:Peptidyl-Dipeptidase A; D019808:Losartan