American Journal of Clinical Nutrition, Vol 24, 1232-1237, Copyright © 1971 by The American Society for Clinical Nutrition, Inc.

Influence of alpha-tocopherol on the inhibition of beta-glucuronidase by peroxidized linoleic acid

¹ From the Department of Nutrition and Food Science, University of Kentucky, Lexington, Kentucky 40506

The in vitro effect of peroxidized linoleic acid on -glucuronidase was studied. Rat liver cell preparation with the nucleus and cell membrane removed served as a source of -glucuronidase. It was incubated at 25 C with peroxidized linoleic acid or its potassium salt, then -glucuronidase activity was determined. Peroxidized linoleic acid or its potassium salt lowered this enzyme activity, but this reduction in activity was partially reversed with time of incubation. The inhibition of -glucuronidase was prevented by -tocopherol or glutathione. Two synthetic antioxidants (butyl hydroxytoluene, butyl hydroxyanisole) had less effect in preventing it. Ascorbic acid had no effect. Cysteine inhibited -glucuronidase. Tocopherol-deficient rat liver preparation tended to have lower -glucuronidase activity (P < 0.10) and higher thiobarbituric acid values (P < 0.01) than that of the control group. The same amount of peroxide inhibited -glucuronidase of the tocopherol-deficient rat liver preparation more than that of control (P < 0.01). Addition of -tocopherol in vitro to tocopherol deficient rat liver preparation prevented this further inhibition of -glucuronidase caused by -tocopherol deficiency. The results suggested that -tocopherol reverses the inhibition of -glucuronidase activity by reacting with the peroxide or an enzyme-peroxide complex.