Two cytochrome P-450 isoforms catalysing O-de-ethylation of ethoxycoumarin and ethoxyresorufin in higher plants.
The O-dealkylating activities of 7-ethoxycoumarin O-de-ethylase (ECOD) and 7-ethoxyresorufin O-de-ethylase (EROD) have been fluorimetrically detected in microsomes prepared from manganese-induced Jerusalem artichoke tubers. Cytochrome P-450 dependence of the reactions was demonstrated by light-reversed CO inhibition, NADPH-dependence, NADH-NADPH synergism and by use of specific inhibitors: antibodies to NADPH-cytochrome P-450 reductase, mechanism-based inactivators and tetcyclasis. Apparent Km values of 161 microM for 7-ethoxycoumarin and 0.4 microM for 7-ethoxyresorufin were determined. O-De-ethylase activity was also detected in microsomes prepared from several other plant species, including wheat, maize, tulip, avocado and Vicia. ECOD and EROD were low or undetectable in uninduced plant tissues, and both activities were stimulated by wounding or by chemical inducers. Two distinct cytochrome P-450 isoforms are involved in ECOD and EROD activities since (1) they showed different distributions among plant species; (2) they showed contrasting inhibition and induction patterns; and (3) ECOD but not EROD activity was supported by cumene hydroperoxide.
Werck-Reichhart
D
D
Laboratoire d'Enzymologie Cellulaire et Moléculaire (CNRS UA 1182), Institut de Botanique, Strasbourg, France.
Gabriac
B
B
Teutsch
H
H
Durst
F
F
D015660:7-Alkoxycoumarin O-Dealkylase / Q000378:metabolism*; D001189:Aryl Hydrocarbon Hydroxylases; D001555:Benzene Derivatives / Q000378:metabolism; D003374:Coumarins / Q000378:metabolism*; D019363:Cytochrome P-450 CYP1A1; D065637:Cytochrome P-450 CYP2A6; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010078:Oxazines / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D013696:Temperature; D014230:Triazoles / Q000378:metabolism*
D001555:Benzene Derivatives; D003374:Coumarins; D065607:Cytochrome P-450 Enzyme Inhibitors; D010078:Oxazines; D014230:Triazoles; C017299:7-ethoxycoumarin; C007649:ethoxyresorufin; C053723:tetcyclacis; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; D015660:7-Alkoxycoumarin O-Dealkylase; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1; D065637:Cytochrome P-450 CYP2A6; C007164:cumene hydroperoxide