title: The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia.
abstract: The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia was re-examined using bovine submaxillary mucin and remodelled antifreeze glycoprotein as substrates. Incubation with desialylated bovine submaxillary mucin, which contains six O-linked core types, indicated that the disaccharide Gal beta1-3GalNAc, which is present in very small amount, was the only glycan released, while the disaccharide GlcNAc beta1-3GalNAc, which is the major structure present, and other disaccharides, were not released. To test whether the core disaccharide Gal beta1-3GalNAc with sialic acid linked alpha2-3 to the Gal or linked alpha2-6 to the GalNAc was released, the enzyme was incubated with remodelled antifreeze glycoprotein containing (1) [3H]NeuAc alpha2-3Gal beta1-3GalNAc and (2) Gal beta1-3[[14C]NeuAc alpha2-6]GalNAc as substrates. No NeuAc-containing trisaccharide 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.
authors.affiliation: Department of Chemistry, University College, Galway, Ireland.
authors.forename: M M
authors.initials: MM
authors.lastname: Brooks
authors.forename: A V
authors.initials: AV
authors.lastname: Savage
mesh_terms: D000818:Animals; D021301:Antifreeze Proteins; D002240:Carbohydrate Sequence; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006596:Hexosaminidases / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009077:Mucins / Q000737:chemistry / Q000378:metabolism*; D019158:N-Acetylneuraminic Acid / Q000737:chemistry / Q000378:metabolism; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013296:Streptococcus pneumoniae / Q000201:enzymology*; D013363:Submandibular Gland / Q000737:chemistry; D013379:Substrate Specificity; D048809:alpha-N-Acetylgalactosaminidase
chemical_list: D021301:Antifreeze Proteins; D006023:Glycoproteins; D009077:Mucins; D006596:Hexosaminidases; D048809:alpha-N-Acetylgalactosaminidase; D019158:N-Acetylneuraminic Acid