Differences in N-acetyllactosamine synthesis between beta-1,4-galactosyltransferases I and V.
Unlike classical beta-1,4-galactosyltransferase (beta-1,4-GalT I), beta-1,4-GalT V (formerly IV**) has little activity towards 1 mM N-acetylglucosamine [Sato et al. (1998) Proc Natl Acad Sci USA 95:472-477]. The human beta-1,4-GalTs I and V were expressed individually in Sf-9 cells by transfection of the full coding sequences, and their N-acetyllactosamine synthetase activities were determined towards different N-acetylglucosamine concentrations. Kinetic studies using the cell homogenates as an enzyme source revealed that beta-1,4-GalTs I and V possess Km values of 0.6 mM and 33 mM towards N-acetylglucosamine, and of 48 microM and 41 microM towards UDP-Gal, respectively. No significant inhibition of N-acetyllactosamine synthesis with alpha-lactalbumin was observed for beta-1,4-GalT V but the significant inhibition with alpha-lactalbumin was observed for beta-1,4-GalT I.
Sato
T
T
Department of Biosignal Research, Tokyo Metropolitan Institute of Gerontology, Japan.
Furukawa
K
K
D000606:Amino Sugars / Q000096:biosynthesis*; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data
D000606:Amino Sugars; D018076:DNA, Complementary; C000458:N-acetyllactosamine; D005700:Galactosyltransferases; C119701:beta-1,4-galactosyltransferase I; C111678:beta-1,4-galactosyltransferase IV