Abstract
A simple and efficient method is described to remove hemoglobin (Hb) from human term placental cytosol to study dioxygenase and co-oxidase activities of lipoxygenase. In the untreated samples, 70% – 80% of the linoleic acid-dependent dioxygenase and co-oxidase activities were found to be associated with the pseudo-lipoxygenase activity of Hb. Zinc sulfate (0.5 mM) precipitated ⪢97% of the Hb present in the cytosol. The dioxygenase activity of the ZnSO4treated cytosol exhibited a Vmaxvalue of 313 nmoles linoleic acid hydroperoxide formed/min/mg protein and a KMof 1.4 mM for linoleic acid. The ZnSO4treated cytosol displayed co-oxidase activity toward benzidine, dimethoxybenzidine, guaiacol, pyrogallol, tetramethylbenzidine and tetramethyl- p -phenylenediamine. Nordihydroguaiaretic acid, 5,8,11-eicosatriynoic acid, butylated hydroxyanisole, butylated hydroxytoluene and gossypol caused concentration dependent inhibition of dioxygenase and co-oxidase activities. These results suggest ZnSO4precipitation of Hb from cytosol does not alter the functional characteristics of the human term placental lipoxygenase.
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