STRUCTURE OF THE b-N-ACETYLHEXOSAMINIDASE REVEALED BY HOMOLOGY MODELING AND VIBRATIONAL SPECTROSCOPY
R. Ettrich1, V. Kopecký Jr.2,3, K. Hofbauerová3,4, V. Baumruk2, V. Křen4 and K. Bezouška3,4
1 Laboratory of High Performance Computing, Institute of Physical Biology of USB and Institute of Landscape Ecology of AS CR, Zámek 136, Nové Hrady, CZ-37333, Czech Republic
2 Institute of Physics, Charles University, Ke Karlovu 5, Prague 2, CZ-12116, Czech Republic
3 Department of Biochemistry, Faculty of Science, Charles University, Albertov 2030, Prague 2, CZ-12840, Czech Republic, email@example.com
4 Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, Prague 4, CZ-14220, Czech Republic
Glycoprotein b-N-acetylhexosaminidase from Aspergillus oryzae catalyses hydrolysis of chitobiose into constituent monosaccharides. The enzyme is physiologically important during the life cycle of fungi . There is an interest in the catalytic mechanism by which these enzymes cleave their substrate since these processes are important in human diseases and control of fungal and insect pests.
Homology modeling with the Modeller program  used the coordinates for a S. marcescens and S. plicatus (enzymes of glycohydrolase family 20 with a 44% degree of similarity). Refinement was achieved through algorithmic analysis and minimization with the TRIPOS force field in the SYBYL/MAXIMIN2 module. The docking of the chitobiose was explored with the DOCK module of SYBYL. The model structure has been confronted with data from FTIR and Raman spectroscopy obtained with the enzyme (both native and deglycosylated form) purified from the medium of the producing organism A. oryzae. The secondary structure determined from analysis of FTIR amide I and II bands and Raman amide I corresponds well to our molecular model. To test thermostability of the enzyme, Raman spectra in the 5–60 °C temperature range were recorded and analyzed by means of factor analysis.
Support from the Ministry of Education of the Czech Republic (No. MSM113100001, No. MSM113200002, No. LN00A141), from the Institutional Research Concept AVOZ5020903, from the Grant Agency of the Czech Republic (grant No. 203/04/1045), and from the Grant Agency of the Academy of Sciences (A5020403) is gratefully acknowledged.
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