Physiol. Res. 54: 395-402, 2005
 


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


2005 by the Institute of Physiology, Czech Academy of Sciences