1998 Fiscal Year Final Research Report Summary
Molecular aspect of drug transport and metabolism by brain carboxylesterases in rats and humans
| Project/Area Number |
09672274
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
医薬分子機能学
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| Research Institution | CHIBA UNIVERSITY |
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Principal Investigator |
HOSOKAWA Masakiyo Chiba University, Faculty of Pharmaceutical Sciences, Lecture, 薬学部, 講師 (70181500)
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| Project Period (FY) |
1997 – 1998
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| Keywords | carboxylesterase / Human brain / cDNA cloning / drug metabolism / prudrug / esterase |
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| Research Abstract |
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
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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
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