Studies on the Respiratory System of Aspergillus oryzae

Abstract

Mitochondria were isolated from young mycelia of Aspergillus oryzae. A set of spring-loaded, counter-rotating rollers of stainless steel were used to disrupt cell walls. The mitochondrial preparation oxidized several intermediates of the tricarboxylic acid cycle and showed distinct respiratory control. Oxygen uptake was strongly inhibited by cyanide and antimycin A. Rotenone or Amytal inhibited oxidation of NAD-linked substraes only incompletely even at higher concentrations than those required for complete inhibition of the oxidation by mammalian mitochondria. NAD-linked substrates produced larger P/O ratios than succinated. Site I phosphorylation seems to occur in contrast to the case with mitochondria from Saccharomyces. 2, 4-Dinitrophenol uncoupled phosphorylation from respiration at a concentration of 10⁻⁴ M. Tri-n-butyl-tin chloride depressed state 3 respiration to the level of state 4 respiration with concomitant lowering of the P/O ratio. Inhibition of state 3 respiration by this reagent was released by 2, 4-dinitrophenol.