Abstract

Mostafa Rezaei-Tavirani, Saeed Hesami-Takallu, Seyed Hassan Moghaddamnia,Shiva Kalantari, Bijan Ranjbar, Seyedeh Zahra Moosavi-Nejad, Sayed-Amir Marashi , Mohammad Rahmati Roodsari and Farhad Malekzad

Adenosine deaminase (ADA) is an important enzyme of the purine metabolic pathway, which catalyzes the conversion of adenosine and deoxyadenosine to their respective inosine derivatives plus ammonia, in a rapid and irreversible reaction. In this work, we studied the structural and kinetic properties of bovine ADA as a function of temperature in the range, 20 - 80°C by circular dichroism (CD) and UVspectrophotometric techniques, as well as by measuring its activity in this temperature range. The results suggest that thermal unfolding of ADA occurs at temperatures above 60°C, while the enzyme undergoes detectable conformational changes during pre-unfolding heating. These changes affect the kinetics of reaction catalyzed by ADA. The relation between enzyme activity and structural changes is discussed.