Enzymatic sulfation of bile salts. Partial purification and characterization of an enzyme from rat liver that catalyzes the sulfation of bile salts.

An enzyme system which catalyzes the transfer of sulfate group from 3'-phosphoadenosine-5'-phosphosulfate to bile salts has been identified and characterized from rat liver. The enzyme is present in the cytosol fraction of liver cells. The apparent Km value for 3'-phosphoadenosine-5'-phosphosulfate was 8 - 10(-6) M andhat for taurolithocholate was 5 - 10(-5) M. Sulfation occurred with conjugated as well as unconjugated bile salts, however, the rate of sulfation was higher with conjugated than unconjugated. The enzyme was present in rat liver and kidney, but not detectable in brain, lung, heart, spleen or intestinal mucosa. The activity is completely inhibited by p-chloromercuribenzoate indicating the enzyme requires a sulfhydryl group for activity. A molecular weight of 130 000 was estimated by gel-filtration technique and the enzyme shows an isoelectric point of 5.3.