Purification and some properties of sulfur:ferric ion oxidoreductase from Thiobacillus ferrooxidans

Abstract

A sulfur:ferric ion oxidoreductase that utilizes ferric ion (Fe3+) as an electron acceptor of elemental sulfur was purified from iron-grown Thiobacillus ferrooxidans to an electrophoretically homogeneous state. Under anaerobic conditions in the presence of Fe3+, the enzyme reduced 4 mol of Fe3+ with 1 mol of elemental sulfur to give 4 mol of Fe2+ and 1 mol of sulfite, indicating that it corresponds to a ferric ion-reducing system (T. Sugio, C. Domatsu, O. Munakata, T. Tano, and K. Imai, Appl. Environ. Microbiol. 49:1401-1406, 1985). Under aerobic conditions, sulfite, but not Fe2+, was produced during the oxidation of elemental sulfur by this enzyme because the Fe2+ produced was rapidly reoxidized chemically by molecular oxygen. The possibility that Fe3+ serves as an electron acceptor under aerobic conditions was ascertained by adding o-phenanthroline, which chelates Fe2+, to the reaction mixture. Sulfur:ferric ion oxidoreductase had an apparent molecular weight of 46,000, and it is composed of two identical subunits (Mr = 23,000) as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sulfur oxidation by this enzyme was absolutely dependent on the presence of reduced glutathione. The enzyme had an isoelectric point and a pH optimum at pH 4.6 and 6.5, respectively. Almost all the activity of sulfur:ferric ion oxidoreductase was observed in the osmotic shock fluid of the cells, suggesting that it was localized in the periplasmic space of the cells.

Glutathione Reductase/Glutathione Is Responsible for Cytotoxic Elemental Sulfur Tolerance via Polysulfide Shuttle in Fungi

“…Bacteria and archaea reduce elemental sulfur. W. succinogenes and Acidianus ambivalens produce quinone-dependent SR (7,41) and P. furiosus as well as Thiobacillus ferroxidans produce NAD(P)H-dependent SR (8,42). Apparently, glutathione is not required for their activity, indicating that the fungi have adapted independently from bacterial and archaeal mechanisms to reduce elemental sulfur during the course of evolution.…”

Purification and Characterization of Sulfide:Quinone Oxidoreductase from an Acidophilic Iron-Oxidizing Bacterium,Acidithiobacillus ferrooxidans

“…Although the transfer of electrons from ferrous iron to oxygen has not been conclusively established, the electron transfer pathway is thought to involve two cytochromes c (Cyc2 and Cyc1), a rusticyanin, and an aa 3 -type cytochrome c oxidase. [4][5][6] On the other hand, although some enzyme activities thought to be involved in the aerobic oxidation of elemental sulfur by A. ferrooxidans were detected, [7][8][9][10][11][12][13][14][15][16] the oxidation pathway of elemental sulfur has not yet been clearly elucidated.…”

Isolation and Characterization ofAcidithiobacillus ferrooxidansStrain D3-2 Active in Copper Bioleaching from a Copper Mine in Chile

“…Tel/Fax: +81-86-251-8306; E-mail: sugio@cc.okayama-u.ac.jp marked difference was observed in the cellular activity of an enzyme involved in the first step of sulfur oxidation in A. ferrooxidans, viz., SFORase. 12,13) A. ferrooxidans strains that showed high SFORase activity also showed high Cu-bioleaching activity. In contrast, strains that showed low SFORase activity showed low Cu-bioleaching activity.…”

“…We have found that both iron oxidase and hydrogen sulfide:ferric ion oxidoreductase (SFORase) [12][13][14][15][16][17][18][19][20] are crucial in Cu-bioleaching by A. ferrooxidans AP19-3, 21) but when the levels of iron oxidase, SFORase, and Cu-bioleaching activities were compared among 67 strains of iron-oxidizing bacteria isolated from natural environments, no significant differences were observed in growth rates in iron medium or in the levels of cellular iron oxidase activity in the cells. However, a y To whom correspondence should be addressed.…”