Effects of β-carotene on soybean lipoxygenase activity: kinetic studies

β-carotene directly influences the amount of soybean lipoxygenase (LOX) in the reaction medium available for the catalytic conversion of linoleic acid into corresponding hydroperoxides. Inhibition of LOX by β-carotene was predominantly of the noncompetitive type. The mean Km(app) value was estimated to be 13.25 μM ±0.15 μM for linoleic acid while the mean Ki value was estimated to be 2.56 μM ±0.14 μM for β-carotene. Vm(app) values decreased from 1.90ΔA234 nm/min to 0.38ΔA234 nm/min as the concentration of β­carotene increased. The IC50 value for β-carotene was 2.49 μM±0.21 μM. It is shown here that β­carotene is an efficient LOX inhibitor, effective at low-level concentration enzyme-dependent peroxidation of linoleic acid. Presence of β-carotene keeps LOX in its reduced form of Fe(II) and the oxidation of linoleic acid is prevented.