Furuya H, Meyer U A, Gelboin H V, Gonzalez F J
Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Mol Pharmacol. 1991 Sep;40(3):375-82.
Sequencing of genomic polymerase chain reaction (PCR) products synthesized using primers generated from the CYP2C8 and CYP2C9 cDNAs revealed the presence of a new CYP2C gene in the human genome. Primers specific to exons of this new gene were used to perform PCR on human liver cDNA libraries and cDNA synthesized from human liver mRNA to generate a cDNA containing a complete cytochrome P450 amino acid reading frame. This cytochrome P450 cDNA, designated CYP2C18, displayed 85% and 87% nucleotide and 77% and 81% amino acid sequence similarities, respectively, with cDNAs and proteins corresponding to CYP2C8 and CYP2C9. cDNA-directed synthesis of CYP2C18 revealed a protein with relative Mr 49,000 on sodium dodecyl sulfate-polyacrylamide gels, which is considerably less than that calculated from the deduced amino acid composition, Mr 55,747. A preferred substrate for this enzyme has not been uncovered. Levels of CYP2C8, CYP2C9, and CYP2C18 mRNAs were examined in 17 human liver specimens using a PCR-based assay. CYP2C18 mRNA was found in all livers examined, albeit at mean levels 7-8-fold lower than those of mRNAs encoding CYP2C8 and CYP2C9. Marked interindividual differences in levels of expression of all three CYP2C mRNAs were also found.
使用从CYP2C8和CYP2C9互补DNA（cDNA）生成的引物合成基因组聚合酶链反应（PCR）产物并进行测序，结果显示人类基因组中存在一个新的CYP2C基因。用该新基因外显子特异性引物对人肝脏cDNA文库以及从人肝脏信使核糖核酸（mRNA）合成的cDNA进行PCR，以生成一个包含完整细胞色素P450氨基酸阅读框的cDNA。这个细胞色素P450 cDNA被命名为CYP2C18，与对应CYP2C8和CYP2C9的cDNA及蛋白质相比，核苷酸序列相似度分别为85%和87%，氨基酸序列相似度分别为77%和81%。CYP2C18的cDNA定向合成产物在十二烷基硫酸钠-聚丙烯酰胺凝胶上显示出相对分子质量（Mr）为49,000的蛋白质，这比根据推导的氨基酸组成计算出的Mr 55,747要小得多。尚未发现该酶的首选底物。使用基于PCR的检测方法在17个人类肝脏标本中检测了CYP2C8、CYP2C9和CYP2C18 mRNA的水平。在所有检测的肝脏中均发现了CYP2C18 mRNA，尽管其平均水平比编码CYP2C8和CYP2C9的mRNA低7至8倍。还发现所有三种CYP2C mRNA的表达水平存在明显的个体差异。
