Cloning and sequencing of the astA gene encoding arylsulfate sulfotransferase from Salmonella typhimurium

Arylsulfate sulfotransferase (ASST) transfers a sulfate group from a phenol ic sulfate ester to a phenolic acceptor substrate. In the present study; th e gene encoding ASST was cloned front a genomic library of Salmonella typhi murium. The gene was subcloned into the vector pKF3 and was sequenced. A re combinant clone harboring the gene was directly identified using a fluoresc ent assay. Sequencing revealed two contiguous open reading frames (ORFs) on the same strand. Based on amino acid sequence homology ORF1 and ORF2 are d esignated as astA and dsbA, respectively: The deduced amino acid sequence o f astA from S. typhimurium was highly similar to those of the Enterobacter amnigenus, Klebsiella, and Campylobacter jejuni ASSTs, encoded by the ast l genes. However, an ASST activity assay revealed a different acceptor speci ficity Using p-nitrophenyl sulfate (PNS) as a donor substrate, phenol is th e best acceptor substrate, followed by alpha -naphthol, resorcinol, tyramin e, acetaminophen, and tyrosine.