Process
Biotechnology |
Microbial
Biotechnology |
Electronic Journal of Biotechnology
ISSN: 0717-3458 |
Vol. 8 No. 2, Issue of August 15, 2005 |
© 2005 by Pontificia Universidad Católica
de Valparaíso -- Chile |
Received December
15, 2004 / Accepted April 27, 2005 |
Chitinase
from Enterobacter sp. NRG4: Its purification, characterization
and reaction pattern
Neetu Dahiya
Department
of Biotechnology
Panjab University
Chandigarh, PIN-160014,
India
Tel: 91 172 2534150
Fax: 91 172 2541409
E-mail:ineetudahiya@yahoo.com
Rupinder Tewari
Department
of Biotechnology
Panjab University
Chandigarh, PIN-160014,
India
Tel: 91 172 2534180
Fax: 91 172 2541409
E-mail:rooptt1@glide.net.in
Ram P. Tiwari
Department
of Microbiology
Panjab University
Chandigarh, PIN-160014,
India
Tel: 91 172 2541770
Fax: 91 1722541409
E-mail: rptiwari@rediffmail.com
Gurinder Singh
Hoondal*
Department
of Microbiology
Panjab University
Chandigarh, PIN-160014,
India
Tel: 91 172 2541770
Fax: 91 172 2541409
E-mail:gshoondal@rediffmail.com
*Corresponding
author
Financial
support: Senior Research Fellowship from Council of Scientific
and Industrial Research (CSIR), Government of India for Neetu Dahiya.
Keywords:
chemical modification, chitinase, Enterobacter sp. NRG4,
purification, substrate binding.
Enterobacter
sp. NRG4 was shown to excrete chitinase into the culture supernatant
when cultivated in medium containing chitin. A 60 kDa extracellular
chitinase was purified to homogeneity and characterized. The enzyme
hydrolyzed swollen chitin, colloidal chitin, regenerated chitin and
glycol chitin but did not hydrolyze chitosan. The chitinase exhibited
Km and Vmax values of 1.43 mg ml-1
and 83.33 µM µg-1 h-1 for swollen chitin, 1.41
mg ml-1 and 74.07 µM µg-1 h-1 for
colloidal chitin, 1.8 mg ml-1 and 40 µM µg-1
h-1 for regenerated chitin and 2.0 mg ml-1 and
33.33 µM µg-1 h-1 for glycol chitin, respectively.
The optimal temperature and pH for activity were 45ºC and pH 5.5, respectively. Mg2+,
K+ and Ca2+ stimulated chitinase activity by
13, 16 and 18%, respectively whereas Cu2+, Co2+,
Ag+ and Hg2+ inhibited chitinase activity by
9.7, 15, 22 and 72.2%, respectively at 1 mM concentration. N-bromosuccinamide
(NBS) at 1 mM and iodoacetamide at 10 mM concentration completely inhibited
the enzyme activity. Dithiobisnitrobenzoic acid (DTNB) at 10 mM concentration inhibited chitinase
activity by 97.2%. Chitin was hydrolyzed to chitobiose and N-acetyl
D-glucosamine when incubated with the purified enzyme. The hydrolysis
pattern of the purified enzyme indicated that the chitinase was an
endochitinase.
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