Study of sensitivity and ability of adenosine deaminase in response to pre-unfolding and especially pathological temperatures via changing the enzyme structure and activity

Abstract

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.