Author/Authors :
Mahinpour، Roya نويسنده Faculty of Chemistry,Department of Biotechnology,University of Kashan,Kashan,Iran , , Ghasemi، Majid نويسنده Faculty of Chemistry,Department of Organic Chemistry,University of Kashan,Kashan,Iran , , Moosavi-Nejad، Zahra نويسنده Faculty of Biological Sciences,Departmentof Biotechnology,Alzahra University,Tehran,Iran , , Zahraie، Zohreh نويسنده Faculty of Chemistry,Department of Biotechnology,University of Kashan,Kashan,Iran ,
Abstract :
The effect of physiological concentrations of caffeine (purified from Persian tea) on adenosine deaminase (ADA) activity at physiological and pathological concentrations of adenosine (as substrate) in 50 mM Tris-HCl buffer (pH 7.3) at 37°C was investigated, using UV-VIS spectroscopy. ADA exhibited a bi-phasic activity behavior and both phases showed positive cooperativities indicating adenosine has at least two regulatory sites on ADA molecule. We proposed a mechanism for the inhibitory effect of caffeine on ADA catalytic activity by analyzing ADA kinetic behavior at various physiological concentrations of caffeine (10, 30, 70 M): Caffeine dominantly resulted in decreased catalytic activity of ADA via reducing the positive homotropic effect of adenosine on ADA activity. Surprisingly, it also showed a very weak but significant activatory effect on ADA activity in a concentration-dependent manner. To the best of our knowledge, this is the first report on the dual effect of caffeine on ADA activity
Keywords :
caffeine , adenosine deaminase , Homotropic effect , Inhibition
