The stoichiometry of oxygen uptake and conjugated diene formation during the dioxygenation of linoleic acid by the pure reticulocyte lipoxygenase. Evidence for aerobic hydroperoxidase activity

Abstract

Simultaneous measurements of oxygen uptake and conjugated diene formation (increase in the absorbance at 234 nm) during the dioxygenation of linoleic acid by the pure reticulocyte lipoxygenase gave a nearly theoretical stoichiometry of 1.1 in a temperature range from 5 to 30°C and a wide range of concentrations of both oxygen and linoleic acid. At low concentrations of either oxygen or linoleic acid or both, secondary processes occurred such as linoleic acid-supported lipohydroperoxidase reactions leading to the disappearence of conjugated dienes and to the formation of oxodienes, linoleic acid dimers and epoxyhydroxy derivatives. Under these conditions marked deviations of the stoichiometry between oxygen uptake and conjugated diene formation appeared. The formation of conjugated oxodienoic fatty acids absorbing at 285 nm occurred only under conditions of high concentrations of linoleic acid and limiting oxygen supply. The results indicate that lipohydroperoxidase reactions catalyzed by the pure reticulocyte lipoxygenase do not only take place under strictly anaerobic conditions but also under conditions of limiting concentrations of either linoleic acid or oxygen or both.