Abstract
The reduction of the triple bond and carbonyl group of an α,β-ketoalkyne, 4-phenyl-3-butyn-2-one (PBYO), by rat liver microsomes and cytosol was investigated. The triple-bond-reduced product trans-4-phenyl-3-buten-2-one (PBO) and the carbonyl-reduced product 4-phenyl-3-butyn-2-ol (PBYOL) were formed when PBYO was incubated with rat liver microsomes in the presence of NADPH. The triple bond of 1-phenyl-1-butyne, deprenyl, ethynylestradiol, ethinamate, and PBYOL, in which the triple bond is not adjacent to a carbonyl group, were not reduced by liver microsomes even in the presence of NADPH. PBO was further reduced to 4-phenyl-2-butanone (PBA) by liver cytosol with NADPH. PBYOL was also formed from PBYO by liver cytosol in the presence of NADPH or NADH. The microsomal triple-bond reductase activity was inhibited by disulfiram, 7-dehydrocholesterol, and 18β-glycyrrhetinic acid but not β-diethylaminoethyldiphenylpropylacetate or carbon monoxide. The triple-bond reductase activity in liver microsomes was not enhanced by several inducers of the rat cytochrome P450 system. These results suggested that the triple-bond reduction is caused by a new type of reductase, not cytochrome P450. The microsomal and cytosolic carbonyl reductase activities were not inhibited by quercitrin, indomethacin, or phenobarbital. Only S-PBYOL was formed from PBYO by liver cytosol. In contrast, liver microsomes produced R-PBYOL together with theS-enantiomer to some extent. Ethoxyresorufin-O-dealkylase activity in rat liver microsomes was markedly inhibited by PBYO and PBO, partly by PBYOL, but not by PBA.
Footnotes
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This work was supported by a grant-in-aid for Scientific Research (C13672343) from the Japan Society for the Promotion of Science.
- Abbreviations used are::
- PBYO
- 4-phenyl-3-butyn-2-one
- PBO
- trans-4-phenyl-3-buten-2-one
- PBA
- 4-phenyl-2-butanone
- PBOL
- trans-4-phenyl-3-buten-2-ol
- EROD
- ethoxyresorufin-O-dealkylase
- PBAOL
- 4-phenyl-2-butanol
- PBYOL
- 4-phenyl-3-butyn-2-ol
- HPLC
- high-performance liquid chromatography
- GC
- gas chromatography
- SKF 525-A
- β-diethylaminoethyldiphenylpropylacetate
- Received September 20, 2001.
- Accepted December 21, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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