Evidence for the Existence of a Sulphur Oxygenase in Sulfolobus brierleyi

Summary: A sulphur-oxidizing enzyme was purified to homogeneity from cell-free extracts of mixotrophically grown cells of sulfolobus brierleyi. The enzyme catalysed the oxidation of elemental sulphur to sulphite and had an MT of 560 000. Only one type of subunit (M/r 35000) could be detected. The pH and temperature optima for activity were 70 0-5 and 65°C respectively and an apparent Km for sulphur was calculated to be 0.05 M. Enzyme assays with 18O-enriched oxygen demonstrated directly that atmospheric oxygen was attached to sulphur. The first detectable reaction product was sulphite. These results provide evidence that sulphur oxidation in S. brierleyi is performed by an enzyme of the oxygenase type.