The Sulfite Oxidase of Thiobacillus ferrooxidans (Ferrobacillus ferrooxidans)

Abstract

The sulfite oxidase (sulfite: cytochrome c oxidoreductase) from sulfur-grown Thiobacillus ferrooxidans was isolated and partially purified, and its properties were studied. The enzyme was purified 7.3-fold and was 75–85% of the protein present. Sulfite oxidase required SO32− for activity, and could use horse heart cytochrome c and ferricyanide as electron acceptors. The molecular weight was 41 500. The enzyme had a Km for sulfite of 0.58 mM with either ferricyanide or cytochrome c as the electron acceptor. The Km for ferricyanide was 0.25 mM. 5′-AMP did not stimulate enzyme activity. Other properties of the enzyme were similar to the enzyme from Thiobacillus thioparus and Thiobacillus novellus. A metabolic scheme of sulfur utilization for energy production in Thiobacillus ferrooxidans is presented.