Molecular aspect of drug transport and metabolism by brain carboxylesterases in rats and humans

羧酸酯酶(CES，E.C.3.1.1.1)在多种内源和外源化合物的降解中起着重要作用，在许多哺乳动物的药物和脂类代谢中发挥重要作用。这种酶还可以作为某些致癌物的代谢激活途径。我们已经报道，人脑CES制剂与人抗肝CES抗体发生免疫交叉反应，并且通过免疫印迹分析，脑CES在胞浆组分中被检测到，而在微体组分中没有被检测到。用免疫组织化学方法和抗人肝CES抗体证实了CES在人脑内皮细胞中的存在，提示在中枢神经系统和肝脏中存在相似的同工酶。脑内的毛细血管内皮细胞作为一个动态接口，将营养物质和药物从循环转移到脑间质液体中。毛细血管内皮细胞CE-…中CES的存在更多的LLS与保护中枢神经系统免受有毒酯类物质侵害的酶相一致，可能是所谓的血脑屏障系统的一个组成部分。本研究通过与人肝CES HU1的CES特异性探针进行空斑杂交，筛选出人脑组织中的lambdagt11文库。分离并测序了多个克隆。克隆的3‘端核苷酸序列包括一个以终止密码子(Tag)终止的开放阅读火焰，其后是一个含有多聚腺苷信号(AATAAA)的非翻译区，以及Poly(A)尾巴。该克隆的氨基酸序列具有许多在大鼠、小鼠、狗和人肝CES同工酶中高度保守的结构特征，包括活性位点序列(GESAGG、NKQEXG、GDHXD)和可能参与特异性二硫键的四个半胱氨酸，以及可能参与特异性二硫键的四个半胱氨酸。众所周知，滞留在内质网(ER)管腔中的蛋白质在其四肽的羧基末端含有滞留信号(HXEL为CES)。然而，人脑CES不包含BR-保留信号。综上所述，我们从人脑文库中克隆了一个新的CES同工酶，该同工酶存在于毛细血管内皮细胞中，可能通过酯键和酰胺键影响药物的脑分布。较少

Carboxylesterases (CES, E.C.3.1.1.1) function in the hydrolysis of a wide variety of endogenous and xenobiotic compounds, and play an important role in drug and lipid metabolism in many mammalian species. This enzyme also serves as a route of metabolic activation of some carcinogens. We have already reported that a human brain CES preparations was immunocross-reactive with a human anti-liver CES antibody, and that the brain CES was detected in cytosolic fractions, and not in microsomal fractions, by immunoblot analysis. The presence of CES specifically in endothelial cells of human brain has been established by immunohistochemistry methods and using an anti-human liver CES antibody, suggesting the presence of similar isozymes in the central nervous system and the liver. Capillary endothelial cells of brain function as a dynamic interface with regard to the transfer of nutrients and drugs from the circulations to brain interstitial fluid. The presence of CESs in capillary endothelial ce … More lls is consistent with the enzyme acting to protect the central nervous system from toxic esters and may be a component of the so-called blood-brain barrier system. In the present study, lambdagt11 library from human brain was screened by plaque hybridization with CES specific probe of human liver CES HU1. Several clones were isolated and sequenced. The nucleotide sequence of 3'-end of the clone included an open reading flame terminating with stop codon (TAG), followed by untranslated region that included a polyadenylation signal (AATAAA), and poly (A) tail. This deduced amino acid sequence of the clone possessed many structural characteristics that are highly conserved among rat, mouse, dog and human liver CES isozymes, including active site sequence (GESAGG, NKQEXG, GDHXD), and four cysteines which may be involved in the specific disulfide bond., four cysteines which may be involved in the specific disulfide bond. It is well known that proteins which are retained in the endoplasmic reticulum (ER) lumen contain the retention signal at their carboxy- terminal of the tetrapeptide (HXEL for CES). However, the human brain CES was not contained an BR-retention signal. In conclusion, we have cloned a novel CES isozyme from human brain library, which CES present in capillary endothelial cells may influence the cerebral distribution of drugs with ester and amide linkage. Less