An exo- β- N-acetylglucosaminidase from Bacillus subtilis B; characterization

Abstract

The highly purified exo- β- N-acetylglucosaminidase (β-2-acetamido-2-deoxy- d-glucoside acetamidodeoxyglucohydrolase (EC 3.2.1.30) of Bacillus subtilis B has a pH Optimum of 5.9 and is most stable at 8.5. Its isoelectric point appears to be pH 3.8 and it has a mol. wt of about 75 000. The results of studies on its ability to attack a wide range of synthetic and natural substrates are given and kinetic data for the hydrolysis of a number of these reported. The K m and V values for p- nitrophenyl-2-acetamido-2-deoxy-β- d-glucopyranoside and O-2- acetamido-2-deoxy-β- d-glucopyranosyl -(1→4)-2- acetamido-3-O-( d-1-carboxyethyl)-2-dexoy- d-glucose are, respectively, 0.15 and 0.018 mM and 14.50 and 32.57 μmoles/min per mg. The rate of hydrolysis of chitin oligosaccharides decreases with increasing molecular size. Neither O-[2- acetamido-3-O-( d-1-carboxyethyl )-2- deoxy-β- d-glucopyranosyl ] (1å4)-acetamido-2-deoxy- d-glucose nor 2-acetamido-2-deoxy-β- d-galactosides, are attacked and from these results and those of inhibition studies it is concluded that the enzyme is entirely specific for substrates with non-reducing N-acetylglucosamine end groups. IN the light of its substrate specificity and other evidence the possibility that this enzyme has a role in cell wall metabolism is discussed.