Role of Polyols in Thermal
Inactivation of Shark Ornithine Transcarbamoylase
E. BELLOCCO1, G. LAGANÀ1,
D. BARRECA1, S. FICARRA1, E. TELLONE1,
S. MAGAZÙ2, C. BRANCA2, A. KOTYK3,
A. GALTIERI1, U. LEUZZI1
1Department of Organic and
Biological Chemistry, University of Messina,
2Department of Physics and INFM, University of
Messina, Messina, Italy and 3Institute
of Physiology, Academy of Sciences of the Czech Republic,
Prague, Czech Republic
Received July 20, 2004
Accepted October 4, 2004
On line available December 9, 2004
Summary
The ability of activity modulators of ornithine
transcarbamoylase (OCT) from the liver of the thresher shark
Alopias vulpinus to stabilize the enzyme against thermal
denaturation was investigated in the tri-buffer at pH 7.8, at
temperatures ranging from 60 to 70 °C, in the presence of
polyhydroxylic molecules such as glycerol and sugars. The study
indicated that in the presence of 0.5 M sugars and 1.6 M
glycerol in the preincubation medium the OCT activity increases.
When trehalose is introduced directly in the reaction mixture in
a range of concentration of 0.25-0.5 M, the activity is lower
than that with maltose, glycerol and buffer alone. Kinetic data
for carbamoyl phosphate and ornithine with and without maltose
and glycerol are similar, whereas trehalose increases the
kinetic values. Arrhenius plots show an increase of activation
energy due to trehalose, whereas values obtained with maltose
and glycerol are similar to the control
Key words
Elasmobranch • Ornithine transcarbamoylase • Thermostability •
Sugars • Polyols
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