TY - JOUR
T1 - Evidence for two ethanol oxidizing pathways in reconstituted mixed-function oxidase systems
AU - Winston, Gary W.
AU - Cederbaum, Arthur I.
N1 - Funding Information:
oxidation was inhibited by a series of 'OH scavengers in a competitive fashion \[1,3\].T he addition of iron-EDTA, which increases the production of OH by microsomes, increased the oxidation of ethanol \[4\]. We found previously that ethanol oxidation by cytochrome P-450 purified from phenobarbital-treated rats was inhibited by a series of .OH scavengers \[5\].I n that study, it was shown that considerable oxidation of ethanol occurred even in the absence of cytochrome P-450 (25 to 50% of the rate found with the complete system) \[5\]. The present study represents an attempt to 'These studies were supported by USPHS Grants AA-04413, 03508 and Research Career Development Award (2K02-AA-00003) from the National Institute on Alcohol Abuse and Alcoholism.
PY - 1983
Y1 - 1983
N2 - The oxidation of ethanol and typical hydroxyl radical scavengers by NADPH-cytochrome P-450 reductase and cytochrome P-450 purified from phenobarbital-treated rats were studied. Ethanol and the scavengers could be oxidized by the reductase system itself. This system was inhibited by superoxide dismutase, competing hydroxyl radical scavengers and desferrioxamine, but stimulated by either EDTA or iron. These results suggest that an iron-catalyzed Haber-Weiss reaction might be involved in the mechanism by which the reductase mediates the oxidation of typical hydroxyl radical scavengers and ethanol. The addition of cytochrome P-450 had no effect on the oxidation of the scavengers, whereas the oxidation of ethanol was enhanced two-to three-fold over the reductase-dependent rate. The oxidation of ethanol was dependent on both the amount of reductase and P-450. There was no effect of competing scavengers, superoxide dismutase or desferrioxamine on the increased rate of ethanol oxidation produced upon addition of cytochrome P-450. Organic hydroperoxides supported the oxidation of ethanol, but not that of the scavengers when added directly to cytochrome P-450. These results suggest that two independent pathways are operative in supporting NADPH-dependent microsomal oxidation of ethanol. One pathway involves hydroxyl radicals which can be generated by the reductase, whereas the other pathway requires the combined presence of both the reductase and cytochrome P-450, and appears to be independent of oxygen radicals.
AB - The oxidation of ethanol and typical hydroxyl radical scavengers by NADPH-cytochrome P-450 reductase and cytochrome P-450 purified from phenobarbital-treated rats were studied. Ethanol and the scavengers could be oxidized by the reductase system itself. This system was inhibited by superoxide dismutase, competing hydroxyl radical scavengers and desferrioxamine, but stimulated by either EDTA or iron. These results suggest that an iron-catalyzed Haber-Weiss reaction might be involved in the mechanism by which the reductase mediates the oxidation of typical hydroxyl radical scavengers and ethanol. The addition of cytochrome P-450 had no effect on the oxidation of the scavengers, whereas the oxidation of ethanol was enhanced two-to three-fold over the reductase-dependent rate. The oxidation of ethanol was dependent on both the amount of reductase and P-450. There was no effect of competing scavengers, superoxide dismutase or desferrioxamine on the increased rate of ethanol oxidation produced upon addition of cytochrome P-450. Organic hydroperoxides supported the oxidation of ethanol, but not that of the scavengers when added directly to cytochrome P-450. These results suggest that two independent pathways are operative in supporting NADPH-dependent microsomal oxidation of ethanol. One pathway involves hydroxyl radicals which can be generated by the reductase, whereas the other pathway requires the combined presence of both the reductase and cytochrome P-450, and appears to be independent of oxygen radicals.
KW - Ethanol oxidation
KW - Hydroxyl radical scavengers
KW - Mixed-function oxidase systems
KW - Reductase system
UR - http://www.scopus.com/inward/record.url?scp=0021174014&partnerID=8YFLogxK
U2 - 10.1016/0091-3057(83)90170-3
DO - 10.1016/0091-3057(83)90170-3
M3 - Article
C2 - 6314373
AN - SCOPUS:0021174014
SN - 0091-3057
VL - 18
SP - 189
EP - 194
JO - Pharmacology Biochemistry and Behavior
JF - Pharmacology Biochemistry and Behavior
IS - SUPPL. 1
ER -