Kitadokoro K, Hagishita S, Sato T, Ohtani M, Miki K
Shionogi Research Laboratories, Shionogi and Co., Ltd., Fukushima-ku, Osaka 553-0002.
J Biochem. 1998 Apr;123(4):619-23. doi: 10.1093/oxfordjournals.jbchem.a021982.
Phospholipase A2 is a key enzyme in a number of physiologically important cellular processes including inflammation and transmembrane signaling. Human secretory phospholipase A2-IIA is present at high concentrations in synovial fluid of patients with rheumatoid arthritis and in the plasma of patients with septic shock. Inhibitors of this enzyme have been suggested to be therapeutically useful non-steroidal anti-inflammatory drugs. The crystal structure of human secretory phospholipase A2-IIA bound to a novel potent indolizine inhibitor (120-1032) has been determined. The complex crystallizes in the space group P3121, with cell dimensions of a = b = 75.8 A and c = 51.3 A. The model was refined to an R-factor of 0. 183 for the intensity data collected to a resolution of 2.2 A. It was revealed that the inhibitor is located near the active site and bound to the calcium ion. Although the binding mode of the 120-1032 inhibitor to human secretory phospholipase A2-IIA is similar to that previously determined for an indole inhibitor LY311299, the specific interactions between the enzyme and the inhibitor in the present complex include the oxycarboxylate group which was introduced in this inhibitor. The oxycarboxylate group in 120-1032 is coordinated to the calcium ion and included in the water-mediated hydrogen bonding to the catalytic Asp49. In addition, the ethyl group in 120-1032 gains hydrophobic contacts with the cavity wall of the hydrophobic channel of the enzyme.
磷脂酶A2是许多生理重要细胞过程中的关键酶，包括炎症和跨膜信号传导。人分泌型磷脂酶A2-IIA在类风湿性关节炎患者的滑液和脓毒性休克患者的血浆中以高浓度存在。该酶的抑制剂已被认为是治疗有用的非甾体抗炎药。已确定人分泌型磷脂酶A2-IIA与新型强效中氮茚抑制剂（120-1032）结合的晶体结构。该复合物在空间群P3121中结晶，晶胞尺寸为a = b = 75.8 Å，c = 51.3 Å。对于收集到2.2 Å分辨率的强度数据，该模型被精修至R因子为0.183。结果显示该抑制剂位于活性位点附近并与钙离子结合。虽然120-1032抑制剂与人分泌型磷脂酶A2-IIA的结合模式与先前确定的吲哚抑制剂LY311299相似，但在当前复合物中酶与抑制剂之间的特定相互作用包括该抑制剂中引入的氧羧酸盐基团。120-1032中的氧羧酸盐基团与钙离子配位，并参与到与催化性天冬氨酸49的水介导氢键中。此外，120-1032中的乙基与酶疏水通道的腔壁形成疏水接触。
