Abstract
The carboxylesterases (CESs) are a family of serine hydrolases that hydrolyze compounds containing an ester, amide, or thioester. In humans, two dominant forms, CES1 and CES2, are highly expressed in organs of first-pass metabolism and play an important role in xenobiotic metabolism. The current study was conducted to better understand species-related differences in substrate selectivity and tissue expression of these enzymes. To elucidate potential similarities and differences among these enzymes, a series of 4-nitrophenyl esters and a series of gemcitabine prodrugs were evaluated using enzyme kinetics as substrates of expressed and purified CESs from beagle dog, cynomolgus monkey, and human genes. For the substrates examined, human and monkey CES2 more efficiently catalyzed hydrolysis compared with CES1, whereas CES1 was the more efficient enzyme in dog. Quantitative real-time polymerase chain reaction and Western blot analyses indicate that the pattern of CES tissue expression in monkey is similar to that of human, but the CES expression in dog is unique, with no detectable expression of CES in the intestine. Loperamide, a selective human CES2 inhibitor, was also found to be a CES2-selective inhibitor in both dog and monkey. This is the first study to examine substrate specificity among dog, human, and monkey CESs.
Footnotes
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.111.041335.
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ABBREVIATIONS:
- CES
- carboxylesterase
- hCES
- human carboxylesterase
- dCES
- dog carboxylesterase
- cCES
- cynomolgus monkey carboxylesterase
- 4NP
- 4-nitrophenol
- 4NPB
- 4-nitrophenyl butyrate
- bis-Tris
- 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol
- PBST
- Dulbecco's phosphate-buffered saline containing 1% Tween 20
- 6NC
- 6-nitrocoumarin
- 4NPTMA
- 4-nitrophenyl trimethylacetate
- 4NPGB
- 4-nitrophenyl 4-guanidinobenzoate
- 4NPDMA
- 4-nitrophenyl dimethylacetate
- 4NPA
- 4-nitrophenyl acetate
- 4NPP
- 4-nitrophenyl propionate
- 4NPV
- 4-nitrophenyl valerate
- PCR
- polymerase chain reaction.
- Received July 1, 2011.
- Accepted September 14, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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