The interaction between beta-carotene and lipoxygenase in plant and animal systems.

The effect of beta-carotene (BC) on the activity of lipoxygenase (LOX) from plant and animal sources has been examined. Soybean lipoxygenase L-2 activity towards linoleate was inhibited by BC by a maximum of 70% at pH 6.5, whereas L-1 activity was little affected at pH 9.0. Lineweaver-Burk plots indicated that BC inhibited LOX activity by mixed competitive/non-competitive mechanisms. Other hydrophobic compounds also inhibited LOX activity; oleic acid and retinol were competitive inhibitors whereas tocopherol acetate and 5,8,11,14-eicosatetraynoic acid (ETYA) were non-competitive inhibitors. Binding studies with L-2 LOX bound to Sepharose indicated BC-binding and inhibition with the immobilized LOX. Activity of LOX from animal sources was also inhibited by BC both towards linoleate and arachidonate.