Dioxygenase and co-oxidase activities of rat hepatic cytosolic lipoxygenase.
The role of rat liver cytosolic lipoxygenase in the metabolism of benzidine was studied using linoleic acid as a cosubstrate. Under optimum assay conditions, cytosolic dioxygenase activity in the presence of 3.5 mM linoleic acid at pH 7.2 was 74.07 +/- 1.43 nmoles/min/mg protein. Benzidine was oxidized at the rate of 3.18 +/- 0.13 nmoles/min/mg cytosolic protein to benzidine diimine at pH 7.2 in the presence of 3.65 mM linoleic acid. Both dioxygenase and co-oxidase reactions were inhibited by nordihydroguaiaretic acid in a concentration-dependent manner. Partially purified preparations of rat liver lipoxygenase, free of hemoglobin, exhibited a dioxygenase activity of 223.1 +/- 65.9 nmoles/min/mg protein and co-oxidase activity of 6.1 +/- 0.5 nmoles/min/mg protein toward benzidine. These results suggest that hepatic lipoxygenase may play an important role in the metabolism of this hepatocarcinogen.
Department of Environmental and Occupational Health, College of Public Health University of South Florida, Tampa 33612.
S K
SK
Roy
A P
AP
Kulkarni
D000818:Animals; D001560:Benzidines / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008041:Linoleic Acids / Q000378:metabolism; D008084:Lipoxygenase / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D010544:Peroxidases / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000201:enzymology
D001560:Benzidines; D008041:Linoleic Acids; D016859:Lipoxygenase Inhibitors; C029876:benzidine; D010544:Peroxidases; D008084:Lipoxygenase; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase