AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 3 374-G381, Copyright © 1988 by American Physiological Society
Role of terminal fucose residues in clearance of human glycosylated alpha-amylase
S. E. Tollefsen and J. L. Rosenblum
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.
Human glycosylated alpha-amylase contains a single biantennary N-linked
oligosaccharide that terminates with the structure Fuc alpha 1,3(Gal beta
1,4)GlcNAc. To examine the role of terminal fucose in the clearance of
alpha-amylase, we used lectin affinity chromatography to isolate an
alpha-amylase fraction that contains two terminal fucoses (one in each
branch of the oligosaccharide) and a fraction from which both terminal
fucoses have been enzymatically removed. In the rat, the rate of clearance
of the radioiodinated fraction with terminal fucoses is rapid (t1/2 = 12
min) and is slowed by mannosylated but not galactosylated bovine serum
albumin. The rate of clearance of the radioiodinated alpha-amylase fraction
with no terminal fucoses is also rapid (t1/2 = 9.5 min), but the clearance
is now slowed by galactosylated bovine serum albumin. These findings
indicate that the fucosylated and defucosylated alpha-amylase fractions are
recognized by different carbohydrate-specific receptors. We conclude
therefore that terminal fucose is the recognition marker that effects the
physiological clearance of this glycoprotein.
