ENZYMATIC SULFATION OF BILE-SALTS - PARTIAL-PURIFICATION AND CHARACTERIZATION OF AN ENZYME FROM THE LIVER OF THE SHARK HETERODONTUS-PORTUSJACKSONI THAT CATALYZES THE SULFATION OF THE SHARK BILE STEROID 5-BETA-SCYMNOL

An enzyme system which catalyses the transfer of the sulfate group fro m 3'-phosphoadenosine-5'-phosphosulfate to the bile steroid 5 beta-scy mnol has been isolated and characterized from the liver of the shark H eterodontus portusjacksoni (Meyer 1793). The enzyme is present in the cytosol fraction of liver cells. It was partially purified by hydroxyl apatite chromatography, molecular sizing by G100-sephadex and isoelect rofocusing electrophoresis. The apparent K-m value for 3'-phosphoadeno sine-5'-phosphosulfate was 4 mu M and that for 5 beta-scymnol, 14 mu M . The enzyme activity is inhibited by iodoacetate and p-chloromercurib enzoate indicating the possible requirement of a sulfhydryl group for activity. The molecular weight of the enzyme was estimated to be 40 kD a by gel filtration. This was verified by running the partially purifi ed material on a native gel and electrophoretically separating two maj or bands corresponding to molecular weights of 40 and 45 kDa, respecti vely. Isoelectric focusing of the purified material resulted in two ma jor bands with pI values of 5.0 and 5.85. Enzymatic activity was found to optimal at a pH of 6.5 with little activity recorded at pH 5.0 and 8.0.