OXIDATIVE PHOSPHORYLATION BY AN ENZYME COMPLEX FROM DISRUPTED BRAIN MITOCHONDRIA

Abstract

Although various attempts have been made to isolate a submitochondrial fraction capable of oxidative phosphorylation, it was not until the recent work of Cooper and Lehninger (1) that any degree of success was achieved. Among the techniques used for disrupting mitochondria have been ultrasonic disintegration, freezing-thawing, dispersion with a variety of chemical agents, and variations in pH values. Although slight oxidative phosphorylation (low P:O) was sometimes achieved (a), such treatment preserved only the oxidative portion of the system. Cooper and Lehninger (1) recently obtained a lipoprotein complex from digitonin extracts of rat liver mitochondria which was considerably more active than intact mitochondria on a weight basis. The present study describes a multienzyme preparation from rat brain mitochondria which is similar to Cooper and Lehninger’s Fraction P-l (1) in many respects, but at the same time exhibits certain distinct differences. After work with a variety of dispersing agents, including digitonin, it was found that the detergent Tritonl yielded the most active and consistent preparations. In addition to oxidizing such substrates as pyruvate and glutamate, the submitochondrial fraction from rat brain yields P: 0 ratios closely approaching those of intact mitochondria.