Endo-β-N-acetylglucosaminidase Acting on Carbohydrate Moieties of Glycoproteins

A purified ovalbumin glycopeptide, Asn-(GlcNAc)2(Man)5was [14C]acetylated in the asparagine moiety. Using the [14C]acetylated glycopeptide as a substrate, an endo-β-N-acetylglucosaminidase was purified 2400-fold from the culture fluid of Diplococcus pneumoniae. The enzyme preparation was practically free from various exoglycosidases and proteases. The enzyme cleaved the di-N-acetylchitobiose structure of the [14C]acetylated glycopeptide, yielding equimolar amounts of [14C]acetyl-Asn-GlcNAc and (Man)5(GlcNAc). The enzyme had a pH optimum of 6.5, with a Kmof 0.25 mmand with a Vmaxof 4.67 µmoles per mg of protein per min toward the substrate.