Two phenol sulfotransferase species from one cDNA: nature of the differences

A phenol sulfotransferase from rat liver (EC 2.8.2.9), expressed in Escherichia coli from a single cDNA, was purified as two separable but catalytically active proteins. The proteins appeared to be identical to each other and to the natural liver sulfotransferase by comparison of their amino acid constitution, amino-terminal end group, and interaction with a polyclonal antibody raised against the liver enzyme. Each of the recombinant forms, alpha and beta, catalyzed the sulfuryl group transfer from 4-nitrophenylsulfate to an acceptor phenol, a reaction in which 3'-phospho-adenosine 5'-phosphate (PAP) is a necessary intermediate. Only form beta, however, catalyzes the physiological transfer of a sulfuryl group from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the free phenol. Evidence is presented that sulfotransferase alpha, but not beta, has 1 mol of PAP tightly bound per enzyme dimer. The ability to utilize PAPS as a sulfate donor could be altered: form alpha could be treated and purified as form beta to acquire the ability to use PAPS, whereas form beta was treated by extended incubation with PAP, lost its ability to use PAPS, and was purified as form alpha.