Full Length Research Paper

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

Mostafa Rezaei-Tavirani^1,2*, Saeed Hesami-Takallu³, Seyed Hassan Moghaddamnia¹, Shiva Kalantari⁴, Bijan Ranjbar⁵,  Seyedeh Zahra Moosavi-Nejad⁶, Sayed-Amir Marashi⁷, Mohammad Rahmati Roodsari² and Farhad Malekzad²

¹Clinical Proteomics Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University (M.C.), Tehran, Iran.

²Skin Research Center, Shahid Beheshti University (M.C.), Tehran, Iran.

³Science and Researches Branch, Islamic Azad University, Tehran, Iran.

⁴Asre-Novin Institute of Research and Industrial Services, Unit 12, No. 38 (Malek Building), Tajrish Sq., Fana-Khosro Ave., Tehran, Iran.

⁵Department of Biophysics, Faculty of Science, Tarbiat Modarres University, Tehran, Iran.

⁶Department of Biology, Faculty of Science, Alzahra University, Tehran, Iran.

⁷IMPRS-CBSC, Max Planck Institute for Molecular Genetics, Berlin, Germany.

*Corresponding author. E-mail: tavirani@sbmu.ac.ir, tavirany@yahoo.com,

Tel and Fax: +98-21-22748836.

Accepted 26^th November,2008

   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.

Key words. Adenosine deaminase (ADA), UV-Vis spectrophotometry, Conformational changes, Circular dichroism (CD), Kinetic study.