Identification of a soluble UDP-Gal: Gal (beta 1-4)Glc (or GlcNAc) (alpha 1-3) galactosyltransferase of bovine colostrum.
A soluble UDP-Gal: Gal (alpha 1-3) galactosyltransferase was first detected in bovine colostrum and this enzyme activity was simply assayed by using rho-nitrophenyl-beta-lactoside (Gal(beta 1-4)Glc-C6H5NO2, rho NP-lactoside) as an acceptor. Treating the radioactive product with alpha- or beta-galactosidase, the radioactivity (greater than 95%) was released by only alpha-galactosidase and was identified as [3H]galactose. This shows that galactosyl residue was alpha-linked to rho-nitrophenyl-beta-lactoside. Methylation, hydrolysis, thin layer chromatography and fluorography of the reaction product (Gal(alpha 1-)-[3H]Gal(beta 1-4)Glc-rho NP) yielded 2,4,6-tri-O-methyl[3H]galactose, indicating that galactosyl residue had been transferred to the carbon-3 position of the terminal nonreducing beta-galactosyl residue in rho-nitrophenyl-beta-lactoside. These results confirmed that the structure of the reaction product was Gal(alpha 1-3)Gal(beta 1-4)Glc-rho NP. The enzyme requires Mn2+ for its activity, and shows pH optimum from 6.5 to 7.5. rho-Nitrophenyl-beta-lactoside and asialo alpha 1-acid glycoprotein were more effective as an acceptor than N-acetyllactosamine. The bovine colostrum (alpha 1-3) galactosyltransferase could not convert human O red cells into B active cells, indicating that this enzyme preparation did not contain the activity to synthesize human blood group B erythrocytes.
Hosomi
O
O
Takeya
A
A
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D003126:Colostrum / Q000201:enzymology*; D005260:Female; D005700:Galactosyltransferases / Q000378:metabolism*; D006020:Glycopeptides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007788:Lactose Synthase / Q000378:metabolism*; D009237:N-Acetyllactosamine Synthase / Q000378:metabolism*
D006020:Glycopeptides; C018069:galactosyltransferase acceptor; D005700:Galactosyltransferases; D007788:Lactose Synthase; C047006:N-acetyllactosaminide alpha-1,3-galactosyltransferase; D009237:N-Acetyllactosamine Synthase