Sulphite: cytochrome c oxidoreductase (sulphite dehydrogenase) was purified 2000-fold from Thiobacillus versutus (A2). The enzyme monomer had a molecular weight of 44000 and a pI value of 4·5 α 0·3. Cytochrome c551 was intimately associated with the enzyme: separation of the two greatly decreased sulphite dehydrogenase activity, which was not restored by remixing them. The enzyme had a pH optimum around pH 8·0, exhibited a Km of 14 µm for sulphite, and was inhibited noncompetitively by phosphate, with a Ki value of 12 mm. It was also inhibited by p-hydroxymercuribenzoate and cyanide. Its involvement in the oxidation of thiosulphate in T. versutus is discussed.
AminuddinM.,
NicholasD. J. D.
1974; An AMP-independent sulphite oxidase from Thiobacillus denitrificans: purification and properties. Journal of General Microbiology 82:103–113
CharlesA. M.,
SuzukiI.1966; Purification and properties of sulfite: cytochrome c oxidoreductase from Thiobacillus novellus.
. Biochimica et biophysica acta 128:522–534
International Union of Biochemistry1979Enzyme Nomenclature. Recommendations (1978) of the Nomenclature Committee of the International Union of Biochemistry on the Nomenclature and Classification of Enzymes New York: Academic Press;
JohnsonJ. L.,
HainlineB. E.,
RajagopalanK. V.1980; Characterization of the molybdenum cofactor of sulfite oxidase, xanthine oxidase and nitrate reductase. Journal of Biological Chemistry 255:1783–1786
KellyD. P.1982; Biochemistry of the chemolitho- trophic oxidation of inorganic sulphur. Philosophical Transactions of The Royal Society. Series B298:499–528
LuW-P.,
KellyD. P.1983a; Thiosulphate oxidation, electron transport and phosphorylation in cell-free systems from Thiobacillus A2. Journal of General Microbiology 129:1661–1671
LuW-P.,
KellyD. P.1983b; Partial purification and resolution of a thiosulphate-oxidizing system from Thiobacillus A2. Journal of General Microbiology 129:1673–1681
LuW-P.,
KellyD. P.1983d; Purification and some properties of two principal enzymes of the thiosulphate-oxidizing multi-enzyme system from Thiobacillus A2. Journal of General Microbiology 129:3549–3564
LuW-P.,
KellyD. P.1984; Purification and characterization of two essential cytochromes of the thiosulphate-oxidizing multi-enzyme system from Thiobacillus A2 (T. versutus).
. Biochimica et biophysica acta in the Press
LyricR. M.,
SuzukiI.1970; Enzymes involved in the metabolism of thiosulfate by Thiobacillus thio- parus. I. Survey of enzymes and properties of sulfite: cytochrome c oxidoreductase. Canadian Journal of Biochemistry 48:334–343
YamanakaT.,
YoshiokaT.,
KimuraK.1981; Purification of sulphite: cytochrome c reductase of Thiobacillus novellus and the reconstitution of its sulphite oxidase system with the purified constituents. Plant and Cel! Physiology 22:613–622