Abstract
The inhibitory effects of barbiturates on the NADH-cytochrome c oxidoreductase enzyme have been studied in respiring mitochondrial and submitochondrial preparations. These included a particulate enzyme derived from sucrose mitochondria and a 0.2% deoxycholate extractable enzyme derived from a Keilin-Hartree particle. Inhibition by the barbiturates has been localized between the enzyme flavoprotein and coenzyme Q-1. Blockade at this site probably involves interaction between the barbiturate, the enzyme and a coenzyme Q-ferrous complex. Other features of the barbiturate inhibition which have been studied are the correlations of lipid solubility and of ability to lower surface tension of water with inhibition of the enzyme. The correlation of inhibition by barbiturates with lipid solubility was high (r = 0.95), whereas the correlation with lowering surface tension was moderate (r = 0.66). Interaction reversibility by amobarbital with respiring particles was shown to be reversible and without effect on subsequent sensitivity to added barbiturate.
Footnotes
- Received June 13, 1968.
- Accepted September 16, 1968.
- © 1969, by The Williams & Wilkins Company