Acceptor specificity and tissue distribution of three human α‐3‐fucosyltransferases

Abstract

Based on the capacity to transfer .alpha.-L-fucose onto type-1 and type-2 synthetic blood group H and sialylated acceptors, a comparison of the .alpha.-3-fucosyltransferase activities of different human tissues is shown. Three distinct acceptor specificity patterns are described: (I) myeloid .alpha.-3-fucosyltransferase pattern, in which leukocytes and brain enzymes transfer fucose actively onto H type-2 acceptor and poorly onto sialylated N-acetyllactosamine; (II) plasma .alpha.-3-fucosyltransferase (EC 2.4.1.152), in which plasma and hepatocyte enzymes transfer, in addition, onto the sialylated N-acetyllactosamine; (III) Lewis .alpha.-3/4-fucosyltransferase (EC 2.4.1.65), in which gall-bladder, kidney and milk enzymes transfer, in addition, onto type-1 acceptors. The small amount (< 10%) of .alpha.-3-fucosyltransferase activity found in the plasma of an .alpha.-3-fucosyltransferase-deficient individual had a myeloid-type acceptor pattern, suggesting that this small proportion of the plasma enzyme is derived from leukocytes. In addition to the three acceptor specificity patterns, these enzyme activities can be differentiated by their optimum pH: 8.0-8.7 for the enzymes from myeloid cells and brain, 7.2-8.0 for liver enzymes and 6.0-7.2 for gallbladder enzymes. Milk samples had two .alpha.-3-fucosyltransferase activities, the Lewis or .alpha.-3/4-fucosyltransferase under control of the Lewis gene and an .alpha.-3-fucosyltransferase with plasma acceptor pattern which was independent of the control of the Lewis gene. The apparent affinity for GDP-fucose of the myeloid-like enzyme was weaker than those of the plasma and Lewis-like enzymes. The apparent affinities for H type 2 and siallyated N-acetyllactosamine were stronger for exocrine secretions as compared to the plasma and myeloid enzymes. The plasma type of .alpha.-3-fucosyltransferase activity was more sensitive to N-ethylmaleimide and heat inactivation than the samples with myeloid-like .alpha.-3-fucosyltransferase activity.