Human milk fucosyltransferase and a-L=fucosidase activities change during the course of lactation Gherman Y. Wiederschain and David S. Newburg Shriver Center for Mental Retardation, Waltham, MA USA and Harvard Medical School, Boston, MA USA Human milk is rich in fucosylated oiigosaccharides and other gfycoconjugates, some of which ufSect inter- actions between pathogens and host cell surface. Two types of enzymes, fucosyltransferase and cx-L-fucosidase. involved in the biosynthesis and degradation of these compounds, were analyzed in random samples of human milk from healthy donors. In mature milk (days 52 to 781, the individual variabitity for fucosyltransferase was twice that offu~osidase. The activities of both enzymes were observed to change over the course of lactation from day 3 to day 370. ot-Fucosyltransferase activity was greatest during the first 30 days of lactation and declined signtficantly between 30 and 100 days. From day 100, fucosyltransferase activity remained nearly constant. Fucosidase activity was high at the onset of lactation followed by a precipitous decline, reaching a nadir by the second week. After the fourth week, the cr-L-fucosidase activity increased in direct proportion to the length of lactation. The possible reiat~on.~h~~ of these enzymes to the faco~lo~igosac&har~de content of human milk are discussed. (J. Nutr. Biochem. 6:582-587, 1995.) Keywords: human milk; fucosyltransferase; cx-L-fucosidase; lactation Introduction Human milk is unique with regard to the content and com- plexity of its glycoconjugates, especially oligosaccharides; many of these oligosaccharides are fucosylated. ’ Some fu- cosyloligosaccharidesare potent inhibitors of bacterial ad- hesion to epithelial surfacesand increaseresistanceto en- teric bacterial toxins in vivo. For example, we found that neutral fucosyloligosaccharide(s) of human milk protect against the stable toxin of Escherichia coli in vivo and in vitro and that fucosyloligosaccharidesinhibit the binding of invasive strains of Ca~pylobacter jejuni to target cells in vitro.2*3 The oligosaccharidecomposition of human milk is This work was supported by the National Institute of Child Health and Human Deveiopment, Grant HD 13021. Part of these data was presented in Experimental Biology 94, April 1994 [FASEB J. 8, A157 (1994)]. Address reprint requests to Dr. David S. Newburg at the Department of Biochemistry, &river Center for Mental Retardation, 200 Trapelo Road, Waltham, MA 02254, USA. Received November 17, 1994; accepted May 12, 1995. known to vary as a function of several parameters including maternal blood group type, secretor status, and stage of lactation. The enzymes involved in the biosynthesis and degradation of fucosyloligosaccharides are fucosyltrans- ferase and or-L-fucosidase . The structural variety of fucosyl residues in oligosaccha- rides is determined by a family of fucosyltransferases(EC 2.4.1.65), which have been detected in a number of sources, including human milk. Their purification ’ 5Jq.y.y; ties, and substratespecificity have been described. major fucosyltransferase of milk is reported to be the o-3/4- fucosyl~ansferase, which hasbeencloned and is referred to as Lewis type fucosyhransferaseIIL6 To our knowledge, there is no information available concerning the levels of fucosyltransferase activity of human milk among healthy individuals and changesin this activity during the courseof lactation. a-L-Fucosidase (EC 3.2.1.5 1) can hydrolyze fucose from fucosyloligosaccharides, changing their structure and biological activity.7.8 Fucosidase is a ubiquitous lysosomal glycosidase found in a wide variety of organisms.9710 The importance of fucosidasein ma~alian metabolism is ev- Nutritional Biochemistry 6:582-587, 1995 0 Elsevier Science Inc. 1995 655 Avenue of the Americas, New York, NY 10010 0955-2863/95/$10.00 SSDI 0955-2863(9.5)00124-I