Aoyama T, Hardwick J P, Imaoka S, Funae Y, Gelboin H V, Gonzalez F J
Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
J Lipid Res. 1990 Aug;31(8):1477-82.
Cytochromes P450IVA1 and IVA3 display 72% amino acid sequence similarity and are expressed in livers of rats treated with the hypolipidemic drug clofibrate. The catalytic activities of IVA1 and IVA3 were examined by cDNA-directed expression using vaccinia virus. cDNA-expressed IVA1 and IVA3 had relative Mrs of 51,500 and 52,000, respectively, on SDS-polyacrylamide gels. Both enzymes displayed reduced, CO-bound absorption spectra with lambda max of 452.5 nm. IVA1 and IVA3 hydroxylated lauric acid at the omega and omega-1 positions with equivalent omega/omega-1 ratios of about 12.5. IVA1 had a substrate turnover of 21 min-1 which was about fourfold higher than that of IVA3. The omega and omega-1 hydroxylation of palmitic acid was also catalyzed by these P450s with combined turnover numbers for both metabolites of 45 min-1 or 18 min-1 for IVA1 and IVA3, respectively. The omega/omega-1 oxidation ratio of IVA1 for palmitate was 1.25 which was almost fourfold higher than that obtained for IVA3. These enzymes also catalyzed omega oxidation of the physiologically important eicosanoids prostaglandins E1 and F2 alpha with turnover numbers of about one-tenth those calculated for fatty acid oxidations. No omega-1 hydroxy metabolites were produced. These studies indicate that the P450 enzymes IVA1 and IVA3 are able to catalyze the oxidations of both fatty acids and prostaglandins.
细胞色素P450IVA1和IVA3的氨基酸序列相似度为72%，在接受降血脂药物氯贝丁酯治疗的大鼠肝脏中表达。使用痘苗病毒通过cDNA定向表达来检测IVA1和IVA3的催化活性。在SDS-聚丙烯酰胺凝胶上，cDNA表达的IVA1和IVA3的相对分子质量分别为51,500和52,000。两种酶均显示出还原型、与一氧化碳结合的吸收光谱，最大吸收波长为452.5nm。IVA1和IVA3在ω和ω-1位羟基化月桂酸，ω/ω-1比率约为12.5。IVA1的底物周转率为21min-1，约为IVA3的四倍。这些P450酶也催化棕榈酸的ω和ω-1羟基化，IVA1和IVA3两种代谢产物的总周转数分别为45min-1或18min-1。IVA1对棕榈酸的ω/ω-1氧化比率为1.25，几乎是IVA3的四倍。这些酶还催化生理上重要的类二十烷酸前列腺素E1和F2α的ω氧化，周转数约为脂肪酸氧化计算值的十分之一。未产生ω-1羟基代谢产物。这些研究表明，P450酶IVA1和IVA3能够催化脂肪酸和前列腺素的氧化。
