Xenobiotic-metabolizing enzyme systems in test fish--II. The ethylmorphine N-demethylase activity of guppy (Poecilia reticulata) liver.
The oxidative demethylation of the model substrate ethylmorphine has been characterized for the first time in the liver of a fish (Poecilia reticulata). The enzyme showed maximal activity at 35 degrees C and pH values higher than 8. The values of Km and Vmax for the reaction were 0.83 +/- 0.11 mM and 4.64 +/- 0.81 nmol HCHO/(mg microsomal protein) per min. The activity is attributed to the cytochrome P-450-dependent monoxygenase system, since it is inhibited by CO and requires NADPH; moreover it is inhibited competitively by alpha-naphthoflavone and non-competitively by metyrapone. The enzyme activity is induced by a two-week treatment of fish with phenobarbital and may be associated with a protein band of Mr 54,000.
Verdina
A
A
Istituto Superiore di Sanità, Department of Comparative Toxicology and Ecotoxicology, Roma, Italy.
De Angelis
G
G
Funari
E
E
Testai
E
E
Vittozzi
L
L
D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D003532:Cyprinodontiformes / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D005037:Ethylmorphine-N-Demethylase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008797:Metyrapone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology*; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D011036:Poecilia / Q000378:metabolism*
D001571:Benzoflavones; C011512:alpha-naphthoflavone; D010089:Oxidoreductases, N-Demethylating; D005037:Ethylmorphine-N-Demethylase; D010634:Phenobarbital; D008797:Metyrapone