Characterization of CPT-11 hydrolysis by human liver carboxylesterase isoforms hCE-1 and hCE-2.
Characterization of CPT-11 hydrolysis by human liver carboxylesterase isoforms hCE-1 and hCE-2.
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发表时间：
2000-03
期刊：
影响因子：
11.2
通讯作者：
R. Humerickhouse;K. Lohrbach;Lin Li;W. F. Bosron;M. Dolan
中科院分区：
文献类型：
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作者：
R. Humerickhouse;K. Lohrbach;Lin Li;W. F. Bosron;M. Dolan
7-Ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxy-camptothecin (irinotecan; CPT-11) is a prodrug activated by carboxylesterase enzymes. We characterized the hydrolysis of CPT-11 by two recently identified human carboxylesterase (hCE) enzymes, hCE-1 and hCE-2. Km and Vmax for hCE-1 and hCE-2 are 43 microM and 0.53 nmol/min/mg protein and 3.4 microM and 2.5 nmol/min/mg protein, respectively. hCE-2 has a 12.5-fold higher affinity for CPT-11 and a 5-fold higher maximal rate of CPT-11 hydrolysis when compared with hCE-1. In cytotoxicity assays, incubation of 1 microM CPT-11 with hCE-2 (3.6 microg/ml) resulted in a 60% reduction in survival of SQ20b cells. No significant reduction in cell survival was observed after incubation of CPT-11 with hCE-1. These data indicate that hCE-2 is a high-affinity, high-velocity enzyme with respect to CPT-11. hCE-2 likely plays a substantial role in CPT-11 activation in human liver at relevant pharmacological concentrations.
