Alpha-lactalbumin induces bovine milk beta 1,4-galactosyltransferase to utilize UDP-GalNAc.
We now report that alpha-lactalbumin (alpha-LA) has a novel effect on bovine milk UDP-Gal:GlcNAc-beta 1,4-galactosyltransferase (beta 1,4-GT) and induces the enzyme to efficiently utilize UDP-GalNAc as a donor. In the presence of alpha-LA the enzyme transfers GalNAc to free GlcNAc to produce GalNAc beta 1-4GlcNAc at a rate 55% of that compared to the rate when UDP-Gal is the donor in the absence of alpha-LA. The stimulation by alpha-LA is dependent on the concentrations of alpha-LA, acceptor, and sugar nucleotide. Interestingly, beta 1,4-GT is unable to transfer Gal-NAc to Glc with or without alpha-LA. alpha-LA also stimulates the transfer of GalNAc from UDP-GalNAc to various chitin oligomers, although the degree of stimulation decreases as the acceptor size increases. Thus, bovine milk beta 1,4-GT has an inherent ability to utilize two different sugar nucleotides and the sugar nucleotide preference is regulatable by alpha-LA.
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Department of Oklahoma Health Sciences Center, Department of Biochemistry and Molecular Biology, Oklahoma City 73190, USA.
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Cummings
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D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D005688:Galactosamine / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007768:Lactalbumin / Q000494:pharmacology*; D008892:Milk / Q000201:enzymology*; D008969:Molecular Sequence Data; D009237:N-Acetyllactosamine Synthase / Q000187:drug effects / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism; D013379:Substrate Specificity; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000378:metabolism*
D009844:Oligosaccharides; D014536:Uridine Diphosphate N-Acetylgalactosamine; D005688:Galactosamine; D007768:Lactalbumin; D009237:N-Acetyllactosamine Synthase; D005947:Glucose; D005944:Glucosamine