PT  - JOURNAL ARTICLE
AU  - Xie, Mingxing
AU  - Yang, Dongfang
AU  - Liu, Lan
AU  - Xue, Bob
AU  - Yan, Bingfang
TI  - Human and Rodent Carboxylesterases: Immunorelatedness, Overlapping Substrate Specificity, Differential Sensitivity to Serine Enzyme Inhibitors, and Tumor-Related Expression
AID  - 10.1124/dmd.30.5.541
DP  - 2002 May 01
TA  - Drug Metabolism and Disposition
PG  - 541--547
VI  - 30
IP  - 5
4099  - http://dmd.aspetjournals.org/content/30/5/541.short
4100  - http://dmd.aspetjournals.org/content/30/5/541.full
SO  - Drug Metab Dispos2002 May 01; 30
AB  - Carboxylesterases hydrolyze numerous endogenous and foreign compounds with diverse structures. Humans and rodents express multiple forms of carboxylesterases, which share a high degree of sequence identity (∼70%). Alignment analyses locate in carboxylesterases several functional subsites such the catalytic triad as seen in acetylcholinesterase. The aim of this study was to determine among human and rodent carboxylesterases the immunorelatedness, overlapping substrate specificity, differential sensitivity to serine enzyme inhibitors, tissue distribution, and tumor-related expression. Six antibodies against whole carboxylesterases or synthetic peptides were tested for their reactivity toward 11 human or rodent recombinant carboxylesterases. The antibodies against whole proteins generally exhibited a broader cross-reactivity than the anti-peptide antibodies. All carboxylesterases hydrolyzed para-nitrophenylacetate and para-nitrophenylbutyrate. However, the relative activity varied markedly from enzyme to enzyme (>20-fold), and some carboxylesterases showed a clear substrate preference. Carboxylesterases with the same functional subsites had a similar profile on substrate specificity and sensitivity toward phenylmethylsulfonyl fluoride (PMSF) and paraoxon, suggesting that these subsites play determinant roles in the recognition of substrates and inhibitors. Among three human carboxylesterases, HCE-1 hydrolyzed both substrates to a similar extent, whereas HCE-2 and HCE-3 showed an opposite substrate preference. All three enzymes were inhibited by PMSF and paraoxon, but they showed a marked difference in relative sensitivities. Based on immunoblotting analyses, HCE-1 was present in all tissues examined, whereas HCE-2 and HCE-3 were expressed in a tissue-restricted pattern. Colon carcinomas expressed slightly higher levels of HCE-1 and HCE-2 than the adjacent normal tissues, whereas the opposite was true with HCE-3. The American Society for Pharmacology and Experimental Therapeutics