Regiospecific hydroxylation of lauric acid at the (ω-1) position by hepatic and kidney microsomal cytochromes P-450 from rainbow trout

Microsomes from liver or kidney of untreated rainbow trout hydroxylated lauric acid specifically at the (ω-1) position. Turnover numbers for liver (2.72 min^-1) and kidney (14.1 min^-1) were decreased seven- and twofold, respectively, following treatment with β-naphthoflavone. Laurate hydroxylation activity from untreated trout hepatic microsomes was sensitive to inhibition by SKF-525A, but was not sensitive to metyrapone and only partially inhibited by α-naphthoflavone. The temperature optimum of laurate (ω-1) hydroxylation in trout liver microsomes was 25-30 °C. The K_m and V_max for (ω-1)-hydroxylaurate formation was 50 μm and 1.63 nmol min^-1 mg^-1, respectively, in liver and 20 μm and 3.95 nmol min^-1 mg^-1, respectively, in kidney from untreated trout microsomes. (ω-1) Hydroxylation of laurate, in both liver and kidney microsomes, was sensitive to an antibody raised against a previously purified cytochrome P-450 isozyme (LM₂) of trout liver microsomes, which has been shown to be active towards aflatoxin B₁. Antibody to the major isozyme of cytochrome P-450 (LM_4b, active towards benzo(a)pyrene) induced by β-naphthoflavone did not inhibit (ω-1) hydroxylation of laurate in microsomes from untreated or ω-naphthoflavone-treated trout.