Cloning of a human UDP-galactose:2-acetamido-2-deoxy-D-glucose 3beta-galactosyltransferase catalyzing the formation of type 1 chains.
Biochemical evidence suggests that the galactosyltransferase activity synthesizing type 1 carbohydrate chains is separate from the well characterized enzyme that is responsible for the synthesis of type 2 chains. This was recently confirmed by the cloning, from melanoma cells, of an enzyme capable of synthesizing type 1 chains, which was shown to have no homology to other galactosyltransferases. We report here the molecular cloning and functional expression of a second human beta3-galactosyltransferase distinct from the melanoma enzyme. The new beta3-galactosyltransferase has homology to the melanoma enzyme in the putative catalytic domain, but has longer cytoplasmic and stem regions and a carboxyl-terminal extension. Northern blots showed that the new gene is present primarily in brain and heart. When transfected into mammalian cells, this gene directs the synthesis of type 1 chains as determined by a monoclonal antibody specific for sialyl Lewisa. A soluble version of the cloned enzyme was expressed in insect cells and purified. The soluble enzyme readily catalyzes the transfer of galactose to GlcNAc to form Gal(beta1-3)GlcNAc. It also has a minor but distinct transfer activity toward Gal, LacNAc, and lactose, but is inactive toward GalNAc.
Kolbinger
F
F
Novartis Pharma AG, Transplantation Preclinical Research, CH 4002 Basel, Switzerland.
Streiff
M B
MB
Katopodis
A G
AG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000201:enzymology; D016466:CHO Cells; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000096:biosynthesis; D002384:Catalysis; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary; D005700:Galactosyltransferases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008545:Melanoma / Q000201:enzymology; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013205:Staphylococcal Protein A / Q000235:genetics / Q000378:metabolism
D002241:Carbohydrates; D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins; D013205:Staphylococcal Protein A; D005700:Galactosyltransferases; C109917:UDP-galactose 2-acetamido-2-deoxy-D-glucose 3-galactosyltransferase