ENHANCEMENT OF RAT LIVER MICROSOMAL OXIDASES BY MAGNESIUM AND A HEAT-STABLE FACTOR FROM SOLUBLE FRACTION

Aldrin epoxidation and ethylmorphine N-demethylation by rat liver microsomes were increased approximately 2-fold when the microsomal incubates were supplemented with Mg++ or the microsomal supernatant. Enhancement was maximal at an Mg++ concentration of 5 mM and the effect was not diminished in the presence of oxalate, citrate, or fluoride. The Mg++ effect was not due to a stimulation of NADPH generation. The enhancing factor in the soluble fraction was destroyed by extraction with 2-butanol but not with acetone, was heat stable (boiling water bath for 10 min), and could be partially purified by fractionation on a gel filtration column. This factor eluted from the column simultaneously with protein, endogenous Mg++, and endogenous glucose 6-phosphate dehydrogenous activity. Although Mg++ and the heat-stable soluble factor possessed some properties in common, there was considerable evidence that the two enhancers acted independently. © 1969.