Mm. Brooks et Av. Savage, THE SUBSTRATE-SPECIFICITY OF THE ENZYME ENDO-ALPHA-N-ACETYL-D-GALACTOSAMINIDASE FROM DIPLOCOCCUS-PNEUMONIA, Glycoconjugate journal, 14(2), 1997, pp. 183-190
The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactos
aminidase from Diplococcus pneumonia was re-examined using bovine subm
axillary mucin and remodelled antifreeze glycoprotein as substrates. I
ncubation with desialylated bovine submaxillary mucin, which contains
six O-linked core types, indicated that the disaccharide Gal beta 1-3G
alNAc, which is present in very small amount, was the only glycan rele
ased, while the disaccharide GlcNAc beta 1-3GalNAc, which is the major
structure present, and other disaccharides, were not released. To tes
t whether the core disaccharide Gal beta 1-3GalNAc with sialic acid li
nked alpha 2-3 to the Gal or linked alpha 2-6 to the GalNAc was releas
ed, the enzyme was Incubated with remodelled antifreeze glycoprotein c
ontaining (1) [H-3]NeuAc alpha 2-3Gal beta 1-3GalNAc and (2) Gal beta
1-3[[C-14]NeuAc alpha 2-6]GalNAc as substrates. No NeuAc-containing tr
isaccharide was released. These results serve to clarify the doubts of
many researchers regarding the activity of this enzyme on some newly-
described core types and on sialylated substrates.