Fe(II)-oxidizing enzyme purified fromThiobacillus ferrooxidans

An Fe(II)-oxidizing enzyme was purified from Thiobacillus ferrooxidans to an electrophoretically homogeneous state. The enzyme showed absorption peaks at 282 and 382 nm and contained 18–20 atoms of non-haem iron and 6 atoms of inorganic sulphide in the molecule. Its molecular weight was determined to be 63 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The enzyme rapidly reduced T. ferrooxidans ferricytochrome c-552 with Fe2+ ions at pH 3.5. Rusticyanin was not reduced by the enzyme with Fe2+ ions, while it was reduced rapidly by the enzyme with the ions in the presence of a small amount of cytochrome c-552.