Stimulation of respiration by 2:4-dinitrophenol

Abstract

The rate of oxidation of alpha-ketoglutarate and succinate by some preparations of blowfly sarcoaomes was markedly increased by 2:4-dinitrophenol, even in the presence of excess hexokinase and glucose. Only preparations isolated from young blowflies in media containing ethylenediaminetetraacetate showed'' this effect. The respiration of sarcosomes isolated from older blowflies, or from younger flies in sucrose medium, was little affected by dinitrophenol. The respiration of heart sarcosomes was also unaffected. In agreement with earlier work of others, it was found that there was a dinitrophenol-resistant phosphoryl-ation step in the oxidation of alpha-ketoglutarate. This is undoubtedly the substrate-linked phosphorylation, involving succinyl-coenzyme A. The phosphovus: alpha-ketoglutarate ratio in the presence of sufficient dinitrophenol completely to inhibit respiratory chain phosphorylation was substantially below the theoretical value of 1, but could be raised to near 1 by the addition of albumin, which did not prevent the inhibition of respiratory chain phosphorylation by dinitrophenol. With some preparations, the increase of respiration brought about by dinitrophenol more than counterbalanced the decrease in the phosphorylation ratios with the result that the rate of phosphorylation was actually increased by dinitrophenol.