title: Phospholipase A2 as a target protein for nonsteroidal anti-inflammatory drugs (NSAIDS): crystal structure of the complex formed between phospholipase A2 and oxyphenbutazone at 1.6 A resolution.
abstract: Phospholipase A(2) (PLA(2); EC 3.1.1.4) is a key enzyme involved in the production of proinflammatory mediators known as eicosanoids. The binding of the substrate to PLA(2) occurs through a well-formed hydrophobic channel. To determine the viability of PLA(2) as a target molecule for the structure-based drug design against inflammation, arthritis, and rheumatism, the crystal structure of the complex of PLA(2) with a known anti-inflammatory compound oxyphenbutazone (OPB), which has been determined at 1.6 A resolution. The structure has been refined to an R factor of 0.209. The structure contains 1 molecule each of PLA(2) and OPB with 2 sulfate ions and 111 water molecules. The binding studies using surface plasmon resonance show that OPB binds to PLA(2) with a dissociation constant of 6.4 x 10(-8) M. The structure determination has revealed the presence of an OPB molecule at the binding site of PLA(2). It fits well in the binding region, thus displaying a high level of complementarity. The structure also indicates that OPB works as a competitive inhibitor. A large number of hydrophobic interactions between the enzyme and the OPB molecule have been observed. The hydrophobic interactions involving residues Tyr(52) and Lys(69) with OPB are particularly noteworthy. Other residues of the hydrophobic channel such as Leu(3), Phe(5), Met(8), Ile(9), and Ala(18) are also interacting extensively with the inhibitor. The crystal structure clearly reveals that the binding of OPB to PLA(2) is specific in nature and possibly suggests that the basis of its anti-inflammatory effects may be due to its binding to PLA(2) as well.
authors.affiliation: Department of Biophysics, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Nagendra
authors.initials: N
authors.lastname: Singh
authors.forename: Talat
authors.initials: T
authors.lastname: Jabeen
authors.forename: Rishi K
authors.initials: RK
authors.lastname: Somvanshi
authors.forename: Sujata
authors.initials: S
authors.lastname: Sharma
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Dey
authors.forename: Tej P
authors.initials: TP
authors.lastname: Singh
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D016503:Drug Delivery Systems; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010113:Oxyphenbutazone / Q000737:chemistry* / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D054467:Phospholipases A2; D011485:Protein Binding; D014757:Viper Venoms / Q000037:antagonists & inhibitors / Q000201:enzymology / Q000378:metabolism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004791:Enzyme Inhibitors; D014757:Viper Venoms; D010741:Phospholipases A; D054467:Phospholipases A2; D010113:Oxyphenbutazone