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Catalytic properties of
three catalases from Kohlrabi (Brassica oleracea
gongylodes)
Hossein Tayefi-Nasrabadi
Faculty of
Veterinary Medicine, University of Tabriz, Tabriz, Iran.
E-mail:
tayefi@tabrizu.ac.ir or
hossein_tayefinasrabadi@yahoo.com Tel:
00-98-411-3290625. Fax: 00-98- 411-3357834.
Accepted
21 January, 2008 |
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Catalase (EC 1.11.1.6) was extracted from kohlrabi bulbs (Brassica
oleracea gongylodes) with 0.05 M
phosphate buffer, pH 7.0. On the basis of kinetic studies
and activity stain for catalase, only three isoenzymes of
catalases were detected in kohlrabi bulbs extract with pH
optima at 4.5, 6.5 and 10. Highest catalytic efficiency (Vmax/Km)
value was found for isoenzyme active at pH 6.5. Isoenzyme
with pH optima at 4.5 was very sensitive to azide and more
resistant to cyanide in comparison to other two isoenzymes
active in kohlrabi bulbs extract. Substrate inhibition was
found only for the isoenzyme active at pH 4.5. Heat
inactivation studies showed a decrease in catalases activity
at temperatures above 50, 60 and 70°C
for isoenzymes active at pH 6.5, 10 and 4.5, respectively.
Key
words:
Kohlrabi, catalase, crude extract, kinetic, isoenzyme,
thermal stability. |
