title: Partial purification and characterization of an esterase acting on the anticancer pro-drugs, 7-ethylcamptothecin derivatives.
abstract: A hydrolytic enzyme which catalyzes hydrolysis of the ester-linkage of a series of 17-O-acyl derivatives of 7-ethylcamptothecin-21-(2-dimethylamino)ethylamide [acyl derivatives of 22E] was purified from rat liver and its properties were characterized. It hydrolyzed the ester-linkage of all 22E derivatives tested as well as p-nitrophenyl acetate at pH 8-9 but had no effect on 7-ethyl-10-[4-(piperidino)-1-piperidino] carbonyloxycamptothecin (CPT-11: irinotecan), unlike CPT-11 converting carboxylesterase, which was previously purified from rat serum [Tsuji T. et al., J. Pharmacobio-Dyn., 14, 341 (1991)]. The enzyme had no effect on either acetyl choline or butyrylcholine. It was inhibited by several organophosphorous compounds such as diisopropyl fluorophosphate (DFP), bis-(p-nitrophenyl)phosphate and paraoxon, but was insensitive to inhibitors specific for choline esterases. These results indicate that this liver esterase is clearly distinct from choline esterase and serum CPT-11 converting enzyme and is able to convert pro-drugs, O-acyl derivatives of 22E, to an antitumor agent.
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000378:metabolism*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004950:Esterases / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D000077146:Irinotecan; D008099:Liver / Q000201:enzymology; D008297:Male; D010179:Pancreas / Q000201:enzymology; D011355:Prodrugs / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D011355:Prodrugs; D000077146:Irinotecan; C051891:7-ethylcamptothecin; D004950:Esterases; D002166:Camptothecin