alpha-L-Fucosyltransferases related to biosynthesis of blood group substances in human Saliva.

alpha-L-Fucosyltransferases were demonstrated in human saliva which catalyze the transfer of L-fucose from GDP-L-[14C]-fucose to oligosaccharides from human milk. An alpha-(1 yields 4)-L-fucosyltransferase that synthesizes lacto-N-fucopentaose II and lacto-N-difucohexaose I from lacto-N-tetraose and lacto-N-fucopentaose I, respectively, was detected in saliva samples of Le(a--b+) secretors and Le(a+b--) non-secretors in which Lea substance was secreted. This enzyme activity was demonstrable neither in saliva samples of Le(a--b--) secretors nor non-secretors. An alpha-(1 yields 2)-L-fucosyltransferase, that synthesizes lacto-N-fucopentaose I from lacto-N-tetraose, was detected in saliva samples from Le(a--b+) secretors which secreted H and Leb substances and from Le(a--b--) secretors which secreted only H substance. An alpha-(1 yields 3)-L-fucosyltransferase was present in all saliva samples of different ABO and Lewis blood groups, irrespective of their ABH secretor status of the donors. The fucosyltransferases in saliva were activated by Mn++ or Mg++ ions, and were inhibited by ATP, GTP and EDTA. They had a broad pH optimum between pH 5.0 and 6.5.