Structure of sulfatides biosynthesized in vitro.

Starting from galactose-(14)C-labeled phrenosine and 3'-phosphoadenosine-5'-phosphosulfate, radioactive sulfatides have been obtained in vitro with a biosynthetic system similar to the one described by McKhann and Ho (Ref. 6). It has thus been proved that exogenous cerebrosides can act as acceptors of sulfate. The specific radioactivity of the synthetic phrenosine used as precursor was sufficiently high to permit the proof of the structure of the resulting sulfatides to be done by methylation on an amount estimated at 0.1 micro g. The sulfate group was found only at C-3 of galactose, the position at which it is located in sulfatides isolated from tissues. This observation indicates the specificity of the sulfotransferase involved in the in vivo synthesis of sulfatides.