Fig 2.

Time course of absorbance changes at 420 nm after mixing thiosulfate or sulfite and ferricyanide in the presence or absence of enzyme. Symbols: ●, thiosulfate and enzyme; ○, thiosulfate and heat-denatured enzyme; □, thiosulfate and water; ▲, sulfite and enzyme; △, only enzyme without substrates. Experiments were carried out at pH 2.5 and 40°C in triplicates in a mixture containing 1 mM ferricyanide, 10 mM Na-thiosulfate or 10 mM Na-sulfite, 50 mM Na-sulfate, and 7 μg of protein ml⁻¹ (Butyl-650M fraction) from A. ferrooxidans ATCC 23270.