Edward L. Wheeler

Two lipoxygenase isoenzymes and an activator in wheat germ

Abstract Two isoenzymes of lipoxygenase have been separated and purified from wheat germ. One isoenzyme was stable under both acid and basic conditions. The other isoenzyme was unstable in alkaline solutions and appeared to separate into two electrophoretically distinct active forms. The reaction rate of the isoenzymes towards linoleic acid appeared to be influenced differently as substrate concentrations were increased. A protein fraction extracted from wheat germ activated wheat and soybean lipoxygenase. The effect of the activator may have been to alter the structure of the substrate to enhance reaction rate.

Microsomal P-450 induction by some secondary products from thermal oxidation of dietary lipids: Epidermal hyperplasia, mutagenicity and cytochrome P-450 activities

Distillable secondary products from roasted fowl were found to be cytotoxic but not mutagenic when assayed with Salmonella typhimurium strains TA98, TA100 and TA1537. A crudely separated fraction of the volatiles produced focal hyperplasia and damage to the epidermis of the backs of mice. The volatiles also caused an apparent synthesis of non-constitutive forms of rat hepatic cytochromes P-450 which metabolize benzo[a]pyrene B [a]P differently from the constitutive P-450.

Kinetics of wheat germ lipoxygenase adsorbed to hydrophobic surfaces

Abstract Lipoxygenase binds to Teflon or epoxy coated surfaces, presumably through a hydrophobic interaction. The kinetics of bound enzyme differ from the kinetics of free enzyme both in the effect of substrate concentration on velocity and in the dependence of the induction time on substrate concentration. The binding site for the product hydroperoxide appears to be masked when the enzyme is bound to hydrophobic surfaces. In vivo kinetic behavior of the enzyme may be more closely approximated by that of adsorbed enzyme than by free enzyme.