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Role of cytochrome P450 in the oxidation of glycerol by reconstituted systems and microsomes
Author(s) -
Clejan Liviu A.,
Cederbaum Arthur I.
Publication year - 1992
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.6.2.1537467
Subject(s) - chemistry , glycerol , biochemistry , microsome , superoxide dismutase , catalase , enzyme
Glycerol can be oxidized by rat liver microsomes to formaldehyde in a reaction that requires the production of reactive oxygen intermediates. Studies with inhibitors, antibodies, and reconstituted systems with purified cytochrome P4502E1 were carried out to evaluate whether P450 was required for glycerol oxidation. A purified system containing phospholipid, NADPH‐cytochrome P450 reductase, P4502E1, and NADPH oxidized glycerol to formaldehyde. Formaldehyde production was dependent on NADPH, reductase, and P450, but not phospholipid. Formaldehyde production was inhibited by substrates and ligands for P4502E1, as well as by anti‐pyrazole P4502E1 IgG. The oxidation of glycerol by the reconstituted system was sensitive to catalase, desferrioxamine, and EDTA but not to superoxide dismutase or mannitol, indicating a role for H 2 O 2 plus non‐heme iron, but not superoxide or hydroxyl radical in the overall glycerol oxidation pathway. The requirement for reactive oxygen intermediates for glycerol oxidation is in contrast to the oxidation of typical substrates for P450. In microsomes from pyrazole‐treated, but not phenobarbital‐treated rats, glycerol oxidation was inhibited by anti‐pyrazole P450 IgG, anti‐hamster ethanol‐induced P450 IgG, and monoclonal antibody to ethanol‐induced P450, although to a lesser extent than inhibition of dimethylnitrosamine oxidation. Anti‐rabbit P4503a IgG did not inhibit glycerol oxidation at concentrations that inhibited oxidation of dimethylnitrosamine. Inhibition of glycerol oxidation by antibodies and by aminotriazole and miconazole was closely associated with inhibition of H 2 O 2 production. These results indicate that P450 is required for glycerol oxidation to formaldehyde; however, glycerol is not a direct substrate for oxidation to formaldehyde by P450 but is a substrate for an oxidant derived from interaction of iron with H 2 O 2 generated by cytochrome P450.—Clejan, L. A.; Cederbaum, A. I. Role of cytochrome P450 in the oxidation of glycerol by reconstituted systems and microsomes. FASEB J. 6: 765‐770; 1992.