OXIDATION OF ELEMENTAL SULFUR BY AN ENZYME SYSTEM FROM THIOBACILLUS NEAPOLITANUS

A soluble cell-free system from Thiobacillus neapolitanus is described which catalyzed the oxidation of elemental sulfur to sulfate with a contamitant uptake of oxygen. The preparation did not require the addition of reduced glutathione (GSH) for its activity and, under certain conditions, GSH and other sulfhydryl compounds exerted inhibitory effects. Thiol-binding reagents inhibited sulfur oxidation indicating an involvement of free sulfhydryl groups. The participation of a heavy-metal pathway of electron transport to oxygen was suggested by the inhibitory effect of NaN3 (i mM). KCN, depending on the conditions of the experiment, either inhibited or stimulated oxygen uptake; these effects are discussed and the properties of this preparation are compared with those of sulfur-oxidizing systems isolated from other thiobacilli. © 1968.