3 DIFFERENT ENDOGENOUS ALPHA-L-FUCOSYL-TRANSFERASES EXPRESSED IN COS CELLS

The monkey kidney COS cell line is frequently used for the transient e xpression of cloned human fucosyltransferase cDNAs in the belief that negligible endogenous expression of fucosyltransferase genes occurs in these cells. In the course of transfection experiments we observed we ak cell surface expression of sialyl-Le(x) and weak fucosyltransferase activity in extracts of control untransfected cells. Since these acti vities could complicate interpretation of the results with the transfe cted genes, a more detailed examination was undertaken that has now re vealed expression of three different fucosyltransferases in the cells. One enzyme, which utilises N-acetyllactosamine as substrate, has a pH optimum of 7.0, is resistant to heat inactivation, and has been tenta tively identified as an alpha(1),3-fucosyltransferase. A second enzyme which acts on asialo-fetuin has a pH optimum of 5.5 and is rapidly in activated by heat; the acceptor sugar and positional linkage of the tr ansferred fucose are not yet established. A third enzyme that utilises asialo-agalacto-fetuin as acceptor is provisionally identified as an alpha 1,6-fucosyltransferase. (C) 1997 Academic Press.