Yamane M, Shimizu S, Abe A, Yamane S
Department of Biochemistry, Tokyo Medical College, Japan.
Cancer Lett. 1998 Jan 9;122(1-2):51-9. doi: 10.1016/s0304-3835(97)00370-4.
The homogenate from Caco-2 cells of day 13 or 15 after subculturing had high omega-hydroxylation activity of docosahexaenoic acid (22:6(n-3)) or arachidonic acid (20:4(n-6)). Activity, maximal at pH 8.0, was inhibited in the presence of CO or metyrapone and in the absence of NADPH. Omega-hydroxylation activity of lauric acid in the homogenate was not detected. Apparent Michaelis constant (Km) values for 22:6(n-3) and 20:4(n-6) were found to be 4 and 7 microM. Omega-hydroxylation activity considerably increased with growth up to day 13 and then decreased until day 20 even though alkaline phosphatase (ALP) and leucine-aminopeptidase (LAP) activity increased with growth to day 20. Metyrapone in cultures caused omega-hydroxylation, ALP and LAP activity to decrease, while sodium butyrate dose-dependently increased that of omega-hydroxylation, ALP and an endogenous endonuclease and decreased lactate dehydrogenase (LDH) activity in culture medium. The omega-hydroxylation system thus appears quite likely to be associated with cytochrome P450, differentiation and/or apoptosis rather than cytotoxic cell death of Caco-2 cells. Substrate specificity, however, differed from that of human cytochrome P450 4A11.
传代培养后第13天或第15天的Caco - 2细胞匀浆对二十二碳六烯酸（22:6(n - 3)）或花生四烯酸（20:4(n - 6)）具有较高的ω-羟化活性。该活性在pH 8.0时最高，在有CO或甲吡酮存在以及无NADPH时受到抑制。未检测到匀浆中月桂酸的ω-羟化活性。发现22:6(n - 3)和20:4(n - 6)的表观米氏常数（Km）值分别为4和7 microM。尽管碱性磷酸酶（ALP）和亮氨酸氨肽酶（LAP）活性随生长至第20天而增加，但ω-羟化活性在生长至第13天之前显著增加，然后在第20天之前下降。培养物中的甲吡酮导致ω-羟化、ALP和LAP活性降低，而丁酸钠剂量依赖性地增加了ω-羟化、ALP和一种内源性核酸内切酶的活性，并降低了培养基中的乳酸脱氢酶（LDH）活性。因此，ω-羟化系统似乎很可能与细胞色素P450、分化和/或凋亡相关，而不是与Caco - 2细胞的细胞毒性死亡相关。然而，底物特异性与人类细胞色素P450 4A11不同。
