In-vitro biosynthesis of sulphatoglycosphingolipids by rat submandibular salivary glands.

A sulphotransferase activity, concentrated mainly in the microsomal fraction, which catalyses the transfer of sulphate group from 3'-phosphoadenosine-5'-phosphosulphate to galactosylceramide and lactosylceramide was demonstrated in rat submandibular and sublingual glands. However, the sulphotransferase activity of this fraction in submandibular glands was about ten times higher than in sublingual glands. Optimum enzyme activity was obtained using the detergent Triton X-100, F-, and Mg2+ at a pH of 6.8. The enzyme did not catalyse the transfer of sulphate to glucosylceramide, trihexosylceramide and triglucosyl glyceroglucolipid. The sulphotransferase exhibited similar affinity for both galactosyl- and lactosylceramide. The apparent Km of the enzyme for galactosylceramide was 3.8 X 10(-5) M, and for lactosylceramide, 4.3 X 10(-5) M. The results of compositional analysis and periodate-oxidation studies of the 35S-labelled products of the enzyme reactions established that in both [35S]-sulphatoglycosphingolipids the sulphate-ester group is located at C-3 of the galactose residue.