Purification and characterization of ATP sulfurylase from the extremely thermophilic archaebacterial sulfate-reducer, Archaeoglobus fulgidus

ATP sulfurylase (sulfate adenylyltransferase, EC 2.7.7.4) was isolated from the recently described extremely thermophilic sulfate-reducing archaebacterium Archaeglobus fulgidus. The enzyme was purified by ammonium sulfate fractionation and FPLC on Phenyl-Sepharose Fast Flow, Mono-Q and Superose 6. The Mr of ATP sulfurylase was estimated at 150 000 by analytical gel filtration on Superose 6. The enzyme exhibited a strong tendency to form catalytically active trimers. The enzyme preparation gave two bands with molecular weights of 50 000 and 53 000 on analysis of SDS-PAGE, suggesting an α2β structure of the monomer. The pH-optimum for activity was 8.0 and the optimum reaction temperature was 90°C. The apparent Km values for adenylylsulfate and yrophosphate were 0.17 mM and 0.13 mM, respectively. The pI of the archaebacterial ATP sulfurylase was 4.3.