Pyridylamino sugar chain as an acceptor for galactosyltransferase.
Pyridylamino asialo-agalacto-biantennary sugar chain (PA-acceptor), prepared from human alpha 1-acid glycoprotein, was incubated with bovine milk galactosyltransferase. Transfer of galactose residues to PA-acceptor was detected by HPLC analysis, and thus PA-acceptor was shown to be useful for galactosyltransferase assay. Moreover, three species of products, i.e. PA-acceptor monogalactosylated on the Man alpha 1-3 branch of the trimannosyl core, PA-acceptor monogalactosylated on the Man alpha 1-6 branch, and digalactosylated PA-acceptor, were separated and identified by reversed-phase HPLC, so we could simultaneously determine the branch specificity (the ratio of galactosylation on Man alpha 1-3 branch to that on Man alpha 1-6 branch) of the galactosyltransferase. We fractionated the bovine milk galactosyltransferase on a DEAE-5PW column and confirmed that there was a heterogeneity in this enzyme preparation. Each fraction was assayed for acceptor specificity (the ratio of the activity towards N-acetylglucosamine to that towards PA-acceptor) and branch specificity using the PA-acceptor. However, we could not detect differences in the specificities among the fractions. In addition, we found that alpha-lactalbumin stimulated the galactosyltransferase activity towards PA-acceptor.
D000631:Aminopyridines / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D005591:Chemical Fractionation; D002851:Chromatography, High Pressure Liquid; D005453:Fluorescence; D005700:Galactosyltransferases; D006020:Glycopeptides; D013056:Spectrophotometry, Ultraviolet
D000631:Aminopyridines; D006020:Glycopeptides; C018069:galactosyltransferase acceptor; D005700:Galactosyltransferases; C032439:alpha-aminopyridine