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Biochemical characterization of coumarin 7-hydroxylase activity in chick embryo liver microsomes

, : Biochemical characterization of coumarin 7-hydroxylase activity in chick embryo liver microsomes. Biochemical Pharmacology 43(2): 363-369

Coumarin occurs naturally in the diet and can induce and inhibit cytochrome P450 enzymes. Hepatic coumarin 7-hydroxylase activity is the major pathway for coumarin metabolism in humans but not in rats, most strains of mice, or other laboratory animals. Coumarin 7-hydroxylase activity and the effects of chemical inhibitors and inducers on this activity were studied in 19-day-old chick embryo liver microsomes. Activity was between 35 and 75 nmol/mg protein/hr which is approximately 2-fold higher than reported for human liver microsomes. The pH optimum was 7.8 and the Km determined by both an ether extraction and a high performance liquid chromatography method was 7.3 +/- 0.9 (+/- SD) microM. Substrate inhibition was evident at coumarin concentrations above 250 microM (activities at 1000 and 4000 microM coumarin were 84 and 40% of Vmax, respectively). The Ki values (+/- SD) for inhibitors of microsomal coumarin 7-hydroxylase activity in vitro were: alpha-naphthoflavone, 46.9 +/- 19.8 nM; metyrapone, 0.8 +/- 0.9 microM; aniline, 12.3 +/- 8.2 microM; cimetidine, 70.9 +/- 27.9 microM; N-nitrosodimethylamine, 0.7 +/- 0.9 mM; and dimethyl sulfoxide, 7.9 +/- 1.9 mM. Treatment of chick embryos with pyrazole (40 mumol) increased coumarin 7-hydroxylase by 50% at 24 hr, but this activity was unaffected by treatment of embryos with 3-methylcholanthrene (2 mumol) or glutethimide (8 mumol). Thus, hepatic coumarin 7-hydroxylase activity in 19-day-old chick embryos is higher than in most laboratory animals and has similar biochemical properties as the enzyme in humans and mice. The chick embryo liver may be a useful system for studies on the biochemical effects of coumarin and the regulation of cytochrome P450-dependent coumarin 7-hydroxylase.


PMID: 1739422

Other references

Green, G.C.; Kuhne, F.A., 1975: Estimating the state of maturation of a banana bunch from meteorological and supporting data. The assumption was made that the weekly maturation rate for bananas varies with the weekly mean temperature according to a sigmoid relationship. A specific response curve was postulated which closely simulated the average emergence-to-harvesting (...

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Harper, J.F., 1983: Antigenic structure of calmodulin: production and characterization of antisera specific for plant calmodulins or Ca2+-replete vs. Ca2+-free calmodulins. Calmodulin was purified from bovine testis and soybean seed, using affinity chromatography on (6-amino-hexyl)-5-chloro-1-naphthylene sulfonamide (W7)-Sepharose. The simple preparation of this affinity medium is presented. Although bovine and soybe...

Dasch, J.M.; Cadle, S.H., 1985: Wet and dry deposition monitoring in southeastern Michigan. Wet and dry deposition as collected by a bucket were measured at 2 sites in southeastern Michigan for 2 yr. The precipitation had an average pH of 4.27 and a SO42- to NO3- ratio of 2.0. Particulate dry deposition velocities of 0.6 cm s-1 for SO42-...

Hassmén, P., 1995: Simple indicators of physical working capacity. Traditional methods used to estimate an individual's physical working capacity have at least one disadvantage in common, namely, the demand for expensive equipment such as cycle ergometers or treadmills. Consequently, the search for suit able...

Petrescu, A.D., 1978: Fructose and dental caries. Revista de Chirurgie, Oncologie, Radiologie, O. R. L., Oftalmologie, Stomatologie. Seria: Stomatologie 25(3): 177-180

Tsai, W-C.; Loh, C-H.; Lin, S-H.; Tsao, Y-T., 2007: The great fortune of misfortune: an unusual cause of gastrointestinal haemorrhage. Digestive and Liver Disease 40(1): 73-73

Scholte, H.R.; Groot, P.H.E., 1975: Organ and intracellular localization of short-chain Acyl-CoA synthetases in rat and guinea-pig. 1. Homogenates of rat epididymal fat pad, heart, kidney, lactating mammary gland, liver, skeletal muscle and small intestinal mucosa have been partitioned into a particulate and supernatant fraction. With reliable marker enzymes for the mitochondr...

Stewart, J., 1911: Medical Inspection Of Schools: Report To The Canadian Medical Association. Canadian Medical Association Journal 1(5): 425-439