Paylor Ben, Holt Sandra, Fowler Christopher J
Department of Pharmacology and Clinical Neuroscience, Umeå University, SE-901 87 Umeå, Sweden.
Pharmacol Res. 2006 Dec;54(6):481-5. doi: 10.1016/j.phrs.2006.07.006. Epub 2006 Aug 7.
Inhibitors of the enzyme fatty acid amide hydrolase (FAAH), the principal enzyme involved in the metabolism of the endogenous cannabinoid anandamide, have potential utility in the treatment of disorders including inflammation and inflammatory pain. The carbamate compound URB597 (3'-carbamoyl-biphenyl-3-yl-cyclohexylcarbamate) potently and selectively inhibits FAAH by forming a covalent bond with a key serine residue of the enzyme. Little is known as to the pH dependency of this inhibition. Using a preincubation time of 10min, URB597 inhibited rat brain anandamide hydrolysis with pI(50) values of 7.19+/-0.02 and 7.75+/-0.06 at pH 6 and 8, respectively. The inhibition was time-dependent, and second order rate constants of approximately 0.15x10(6)M(-1)min(-1) (pH 6) and approximately 1.2x10(6)M(-1)min(-1) (pH 8) could be estimated. In intact C6 glioma cells and using a preincubation time of 10min, URB597 inhibited the hydrolysis of 250nM [(3)H]AEA hydrolysis with pI(50) values of 5.58+/-0.07 and 6.45+/-0.07 at extracellular pH values of 6 and 8, respectively. Since tissue pH is affected by inflammation, these data would suggest that the pH selectivity of the inhibition can contribute to the potency of the compound in vivo.
脂肪酸酰胺水解酶（FAAH）是参与内源性大麻素花生四烯乙醇胺代谢的主要酶，其抑制剂在治疗包括炎症和炎性疼痛在内的疾病方面具有潜在效用。氨基甲酸酯化合物URB597（3'-氨基甲酰基-联苯-3-基-环己基氨基甲酸酯）通过与该酶的一个关键丝氨酸残基形成共价键，有效且选择性地抑制FAAH。关于这种抑制作用的pH依赖性知之甚少。在预孵育时间为10分钟的情况下，URB597在pH 6和8时分别以7.19±0.02和7.75±0.06的pI(50)值抑制大鼠脑花生四烯乙醇胺水解。这种抑制是时间依赖性的，并且可以估计出在pH 6时约为0.15×10(6)M(-1)min(-1)，在pH 8时约为1.2×10(6)M(-1)min(-1)的二级速率常数。在完整的C6胶质瘤细胞中，预孵育时间为10分钟时，URB597在细胞外pH值为6和8时分别以5.58±0.07和6.45±0.07的pI(50)值抑制250nM [(3)H]AEA的水解。由于组织pH受炎症影响，这些数据表明抑制作用的pH选择性可能有助于该化合物在体内的效力。
