Partial Purification and Characterization of an Endo-α-N-acetylgalactosaminidase from the Culture Medium of Diplococcus pneumoniae1

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Abstract
The culture medium of Diplocuccus pneumoniae contains enzymic activity that cleaves Galβ1↑3GalNAc from desialized human erythrocyte membrane glycoprotein. The enzyme was purified 180-fold by ammonium sulfate fractionation, gel filtration through a Sephadex G-200 column, and DEAE A-25 Sephadex chromatography. The purified enzyme liberates Galβ1↑3GalNAc from glycopeptides and glycoproteins with Galβ1↑3GalNAcαl↑Ser and Thr moieties. The optimum pH of this enzyme is 6.0. Using glycopeptides obtained by trypsin digestion of human erythrocyte membrane glycoprotein as a substrate, a Km of 0.020 mM (on the basis of the amount of Galβ1↑3GalNAc residues) was obtained. So far, the enzyme appears to have a strict specificity for Galβ1↑3GalNAcαl↑Ser and Thr structures, because no oligosaccharides larger than trisaccharides were liberated from porcine submaxillary mucin.