Beta-N-acetylglucosaminidase from Aspergillus nidulans which degrades chitin oligomers during autolysis.
A hexosaminidase from autolyzed cultures of Aspergillus nidulans was purified 196 fold and characterized as a beta-N-acetylglucosaminidase (EC 3.2.1.30). The enzyme has a MW of 190000, a pI of 4.3, and optimum pH of 5.0 and is unstable at temperatures above 50 degrees C. The enzyme is a glycoprotein with 19.5% sugars, mannose being the principal component. It binds strongly to chitin. The enzyme hydrolyzes different substrates. The Ki with the competitive inhibitor 2-acetamido-2-deoxy-D-gluconolactone was independent of the substrate used. The enzyme was inhibited by Hg2+, Ag+, acetate and other organic anions. The kinetics of hydrolysis of chitin oligosaccharides from 2 to 6 units was studied by HPLC. This enzyme is an exoenzyme which degraded chitin oligomers gradually with the production of N-acetylglucosamine. The hydrolysis of N-N'-diacetylchitobiose was inhibited non-competitively by glucosamine and N-acetylglucosamine. In mixtures of chitin oligosaccharides, the hydrolysis of chitobiose was competitively inhibited by each of the other oligomers.
Reyes
F
F
Centro de Investigaciones Biológicas, Unidad de Microbiologia Aplicada, CSIC, Madrid, Spain.
Calatayud
J
J
Vazquez
C
C
Martínez
M J
MJ
D000118:Acetylglucosaminidase / Q000378:metabolism*; D001233:Aspergillus nidulans / Q000201:enzymology*; D002686:Chitin / Q000378:metabolism*; D006596:Hexosaminidases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013379:Substrate Specificity
D002686:Chitin; D006596:Hexosaminidases; D000118:Acetylglucosaminidase