ISOLATION OF THE TETRATHIONATE HYDROLASE FROM THIOBACILLUS-ACIDOPHILUS

An enzyme capable of hydrolysing tetrathionate was purified from cell- free extracts of Thiobacillus acidophilus. The purified enzyme convert s tetrathionate into thiosulfate, sulfur and sulfate. In addition, pen tathionate could also be converted by the same enzyme. Measurement of the enzyme activity during purification is based on the absorbance of the initial intermediates formed from tetrathionate in the ultraviolet region, which have not been identified. Enzyme activity could also be measured by the scattering of insoluble sulfur in the visible region. The purified enzyme has a pH optimum of 2.5 and a temperature optimum of 65 degrees C. Enzyme activity is strongly stimulated by the presen ce of sulfate ions. The purified enzyme is a dimer with two identical subunits of 48 kDa. The ultraviolet-visible absorption spectra and den aturation experiments indicate the presence of an organic cofactor.