Cyanide-resistant respiration in isolated Asparagus mesophyll cells

Abstract

The inhibitors of oxidative phosphorylation antimycin A (0.5 .mu.g/ml), oligomycin (0.01 mg/ml), and sodium azide (3 mM) eliminated energy-dependent H+ efflux from isolated Asparagus mesophyll cells. Antimycin A and oligomycin also reduced ATP levels by 60% or more. In contrast the same concentrations of inhibitors had little or no effect on respiratory O2 consumption. The sequential addition of potassium cyanide to give a final concentration of 5.2 .mu.M resulted in a 60% maximum inhibition of O2 consumption. Subsequent addition of 0.2 mM disulfiram (tetraethylthiuram disulfide), a potent inhibitor of cyanide-resistant respiration, resulted in a further reduction of the O2 consumption rate. In the absence of cyanide, 0.2 mM disulfiram inhibited O2 consumption by 40-80%, depending on the suspension medium. Disulfiram had little or no effect on the ATP levels which varied between 0.7 and 2.2 nmol ATP/106 cells. Disulfiram inhibits a non-energy-conserving cyanide-resistant alternative pathway in Asparagus mesophyll cells.