Cloning of cytochrome P-450 2C9 cDNA from human liver and its expression in CHL cells.

Aim: Using bacterial, yeast, or mammalian cell expressing a human drug metabolism enzyme would seem good way to study drug metabolism-related problems. Human cytochrome P-450 2C9(CYP2C9) is a polymorphic enzyme responsible for the metabolism of a large number of clinically important drugs. It ranks among the most important drug metabolizing enzymes in humans. In order to provide a sufficient amount of the enzyme for drug metabolic research, the CYP2C9 cDNA was cloned and expressed stably in CHL cells.

Methods: After extraction of total RNA from human liver tissue, the human CYP2C9 cDNA was amplified with reverse transcription-polymerase chain reaction (RT-PCR), and cloned into cloning vector pGEM-T. The cDNA fragment was identified by DNA sequencing and subcloned into a mammalian expression vector pREP9. A transgenic cell line was established by transfecting the recombinant vector of pREP9-CYP2C9 into CHL cells. The enzyme activity of CYP2C9 catalyzing oxidation of tolbutamide to hydroxy tolbutamide in S9 fraction of the cell was determined by high performance liquid chromatography(HPLC).

Results: The amino acid sequence predicted from the cDNA segment was identical to that of CYP2C9*1, the wild type CYP2C9. However, there were two base differences, i.e. 21T>C, 1146C>T, but the encoding amino acid sequence was the same, L7, P382. The S9 fraction of the established cell line metabolizes tolbutamide to hydroxy tolbutamide; tolbutamide hydroxylase activity was found to be 0.465 +/- 0.109 micromol.min(-1).g(-1) S9 protein or 8.62 +/- 2.02mol.min(-1).mol(-1) CYP, but was undetectable in parental CHL cell.

Conclusion: The cDNA of human CYP2C9 was successfully cloned and a cell line of CHL- CYP2C9, efficiently expressing the protein of CYP2C9, was established.