Purification and characterization of a thermostable and highly specific ß-N-acetyl-D-glucosaminidase from Aspergillus niger 419

PERA, LICIA MARÍA; INFANTE MARÍA VERÓNICA; BAIGORI, MARIO DOMINGO

BIOTECHNOLOGY AND APPLIED BIOCHEMISTRY

Portland Press

Lugar: Great Britain; Año: 1997 vol. 26 p. 183 - 187

0885-4513

After a 10.5-fold purification, ß-N-acetyl-D-gluco-saminidase (EC 3.2.1.52) produced by Aspergillus niger 419, showed the following main characteristics: maximum activity at 65 ° C, pH 4.5; Km and kcat using p-nitrophenyl-N-acetyl-b-D-glucosaminide as substrate, 0.2 mM and 0.93 X 104 min - 1, respectively; Ea, 30.5 kJ/mol; molecular mass, 131000 Da; pI 4.4. The activity after heating for 15 min at 70, 75 and 80 ° C was 70, 28 and 13% of that found at 65 ° C, respectively. The enzyme was active in reaction mixtures containing glycerol, ethanol, methanol, propan-2-ol, acetone or dioxan. The presence of Sr2 + or Ca2 + enhanced the activity, while it was inhibited by Cu2 + and Fe3 + . The enzyme was highly specific for p-nitrophenyl N-acetyl-b-D-glucosaminide and no activity was found when p-nitrophenyl derivatives of N-acetyl-ß-D-galactosaminide, ß-D-galactopyranoside and ß-D-N,N -diacetylchitobiose were tested as substrates. Due to its thermostability, specificity and resistance to different organic solvents, the enzyme might be a potentially useful tool for the analysis and production of oligosaccharides.