Kinetic and Structural Analysis of the Inhibition of Adenosine Deaminase by Acetaminophen

Abstract

Kinetic and thermodynamic studies have been made on the effect of acetaminophen on the activity and structure of adenosine deaminase in 50 mM sodium phosphate buffer pH 7.5, at two temperatures of 27 and 37°C using UV spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. Acetaminophen acts as a competitive inhibitor at 27°C (Ki=126 μM) and an uncompetitive inhibitor at 37°C (Ki=214 μM). Circular dichroism studies do not show any considerable effect on the secondary structure of adenosine deaminase by increasing the temperature from 27 to 37°C. However, the secondary structure of the protein becomes more compact at 37°C in the presence of acetaminophen. Fluorescence spectroscopy studies show considerable change in the tertiary structure of the protein by increasing the temperature from 27 to 37°C. Also, the fluorescence spectrum of the protein incubated with different concentrations of acetaminophen show different inhibition behaviors by the effector at the two temperatures.

Keywords: :

• Adenosine deaminase
• Acetaminophen
• Competitive inhibition
• Uncompetitive inhibition
• Circular dichroism
• Fluorescence