Identification and characterization of an UDP-Gal: N-acetyllactosaminide alpha-1,3-D-galactosyltransferase in calf thymus

Eur J Biochem. 1983 Aug 15;134(3):523-30. doi: 10.1111/j.1432-1033.1983.tb07598.x.

Abstract

Calf thymus was found to contain a high activity of a galactosyltransferase, which transfers galactose from UDP-galactose to asialo-alpha 1-acid glycoprotein and N-acetyllactosamine. By means of competition and acceptor-specificity studies the enzyme could be distinguished from an N-acetylglucosaminide beta-1,4-galactosyltransferase and an N-acetylgalactosamine-protein beta-1,3-galactosyltransferase, which in addition occur in calf thymus, as well as from the blood-group-B-associated alpha-galactosyltransferase. Identification of the products revealed that the enzyme accomplishes an alpha 1 leads to 3 linkage resulting in a terminal Gal(alpha 1 leads to 3)Gal(beta 1 leads to 4)GlcNAc sequence. The enzyme is membrane-bound and is activated by Triton X-100. It shows optimal activity over a broad pH range (5.5-7.0) and has a pronounced requirement for Mn2+ ions (Km = 6.1 mM) for its action. It is suggested that the alpha-1,3-galactosyltransferase functions in the biosynthesis of calf thymocyte cell-surface glycoconjugates including glycoproteins.

MeSH terms

  • Animals
  • Cattle
  • Chemical Phenomena
  • Chemistry
  • Chromatography, Thin Layer
  • Galactosyltransferases / classification
  • Galactosyltransferases / isolation & purification*
  • Glycoproteins / isolation & purification
  • Hydrogen-Ion Concentration
  • Hydrolysis
  • Methylation
  • Molecular Weight
  • Thymus Gland / enzymology*

Substances

  • Glycoproteins
  • Galactosyltransferases
  • N-acetyllactosamine alpha-D-galactosyltransferase