Cloning, sequence analysis, and characterization of theastA gene encoding an Arylsulfate sulfotransferase fromCitrobacter freundii

Arylsulfate sulfotransferase (ASST) transfers a sulfate group from a phenolic sulfate ester to a phenolic acceptor substrate. In the present study, the gene encoding ASST was cloned from a genomic library copy ofCitrobacter freundii, subcloned into the vector pGEM3Zf(-) and sequenced. Sequencing revealed two contiguous open reading frames (ORF1 and ORF2) on the same strand and based on amino acid sequence homology, they were designated asastA anddsbA, respectively. The amino acid sequence ofastA deduced fromC. freundii was highly similar to that of theSalmonella typhimurium, Enterobacter amnigenus, Klebsiella, Pseudomonas putida, andCampylobacter jejuni, encoded by theastA genes. However, the ASST activity assay revealed different acceptor specificities. Usingp-nitrophenyl sulfate (PNS) as a donor substrate, α-naphthol was found to be the best acceptor substrate, followed by phenol, resorcinol,p-acetaminophen, tyramine and tyrosine.