Occurrence of Two Fucosyltransferase Activities at the Outer Surface of Rat Lymphocytes

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Abstract
To demonstrate the existence of ectofucosyltransferase activities on the outer surface of rat lymphocytes, fucosyltransferase activities were measured on whole cells using procedures enabling the exclusion of the possibility of misleading results due to precursor hydrolysis and intracellular utilization of the free fucose. The contamination by intracellular enzymes freed by the small percentage of broken cells was considered. The described ectofucosyltransferases are able to catalyze the transfer of fucosyl residues from GDP-fucose to the endogenous membrane acceptros but the transfer activity towards exogenous acceptors is restricted to low MW compounds. Use of galactose and di-N-acetylchitobiose as exogenous acceptors and concomitant study of the specific inhibition by N-ethylmaleimide enabled the detection of the following ectofucosyltransferases: a GDP-fucose:galactoside ectofucosyltransferase and a GDP-fucose:N-acetylglucosaminide ectofucosyltransferase.