f Purification and partial characterization of thiosulphate dehydrogenase from Thiobacillus acidophilus
- Authors: Rogier Meulenberg, Jack T. Pronk*, Wim Hazeu, Johannes P. van Dijken, Johannes Frank, Piet Bos, J. Gijs Kuenen
- *Author for correspondence. Tel. 15 782387; fax 15 782355.
- First Published Online: 01 September 1993, Microbiology 139: 2033-2039, doi: 10.1099/00221287-139-9-2033
- Subject: Biochemistry
- Issue Published:
SUMMARY: Thiosulphate dehydrogenase (EC 22.214.171.124; thiosulphate:acceptor oxidoreductase) was purified to apparent homogeneity from Thiobacillus acidophilus by a combination of ammonium sulphate precipitation, hydrophobic interaction chromatography, anion-exchange chromatography and gel filtration. The enzyme catalysed the oxidation of thiosulphate (S2O2- 3) to tetrathionate (S4O2- 6) with potassium ferricyanide as an artificial electron acceptor. The molecular mass of the native enzyme, as determined by gel filtration, was 102 ± 4.2 kDa. The enzyme contained two different subunits with a molecular mass of 24 ± 0.9 and 20 ± 1.0 kDa (SDS-PAGE), respectively. Both subunits contained c 553-type haem with absorption bands at 553, 524 and 416 nm. A 77 K spectrum of purified thiosulphate dehydrogenase revealed that the absorption at 553 nm is due to different haem groups. A cytochrome content of 5.3 mole c-type haem per mole of native enzyme was calculated. The pH optimum of the purified enzyme was 3. Apart from ferricyanide, Wurster's blue (the free radical of tetramethyl p-phenylenediamine) and horse heart cytochrome c could also serve as electron acceptors, though less effectively than ferricyanide. At pH 7.0, the K m for thiosulphate was 0.54 mM. The K m could not be determined at the pH optimum due to the chemical reactivity of thiosulphate at low pH values. Sulphite was a potent inhibitor of enzyme activity.
© Society for General Microbiology 1993 | Published by the Microbiology Society
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