The lactose analog GalNAcbeta1-->4Glc is present in bovine colostrum. Enzymatic basis for its occurrence. |
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| Authors: | I M Van den Nieuwenhof W E Schiphorst D H Van den Eijnden |
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| Institution: | Department of Medical Chemistry, Faculty of Medicine, Vrije Universiteit, Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands. im.van_den_nieuwenhof.medchem@med.vu.nl |
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| Abstract: | We have isolated from bovine colostrum the lactose analog GalNAcbeta1-->4Glc. The enzymatic basis for its occurrence was studied by assaying the activities of GlcNAcbeta-R beta4-N-acetylgalactosaminyltransferase (beta4-GalNAcT) and GlcNAcbeta-R beta4-galactosyltransferase (beta4-GalT) in primary milk and several lactating bovine mammary gland fractions. As the beta4-GalNAcT, which appears to be tightly membrane bound, is induced by the milk protein alpha-lactalbumin (alpha-LA) to act on Glc, it is concluded that beta4-GalNAcT is responsible for the synthesis of GalNAcbeta1-->4Glc in the gland. The comparatively low level (15-20 mg/l) at which this disaccharide is produced may be due to the relatively poor interaction of beta4-GalNAcT with alpha-LA as well as to the fact that alpha-LA does not inhibit the action of the enzyme on N-acetylglucosaminides. |
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