Abstract

Mostafa Rezaei-Tavirani1,2*, Saeed Hesami-Takallu3 , Seyed Hassan Moghaddamnia1 , Shiva Kalantari4 , Bijan Ranjbar5 , Seyedeh Zahra Moosavi-Nejad6 , Sayed-Amir Marashi7 , Mohammad Rahmati Roodsari2 and Farhad

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 UV-spectrophotometric 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.