Characterization of Celecoxib and Valdecoxib Binding to Cyclooxygenase

• DOI: 10.1124/mol.63.4.870
• Publication Date: 2003-03-18T18:52:52Z
• Authors: William F. Hood; James K. Gierse; Peter C. Isakson; James R. Kiefer; Ravi G. Kurumbail; Karen Seibert; Joseph B. Monahan
• Keywords: Valdecoxib; Celecoxib; Dissociation constant

Two compounds (celecoxib and valdecoxib) from the diarylheterocycle class of cyclooxygenase inhibitors were radiolabeled used to characterize their binding cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), several single-point variants COX-2 (Val523Ile, Tyr355Ala, Arg120Ala, Arg120Gln, Arg120Asn) one triple-point variant [Val523Ile, Arg513His, Val434Ile (IHI)]. We demonstrate highly specific saturable these COX-2. Under same assay conditions, little or no COX-1 could be detected. The affinity [(3)H]celecoxib for (K(D) = 2.3 nM) was similar [(3)H]valdecoxib 3.2 nM). seems both rapid slowly reversible with association rates 5.8 x 10(6)/M/min 4.5 dissociation 14 10(-3)/min (t(1/2) 50 min) 7.0 98 [(3)H]valdecoxib, respectively. These increased (4- 11-fold) when charged arginine residue located at entrance main hydrophobic channel mutated smaller uncharged amino acids (Arg120Ala, Arg120Asn). Mutation residues within active site that define a 'side pocket' (Tyr355Ala, Val523Ile, IHI) had greater effect on rate than rate. mutations, which modified shape access pocket', affected more [(3)H]celecoxib. studies provide direct insight into properties constants celecoxib valdecoxib