Purification and characterization of adenosine deaminase from camel skeletal muscle

Abstract

Adenosine deaminase was purified (780-fold) from skeletal muscle of camel ( Camelus Dormedarius) to homogeneity level by using DEAE Sephadex chromatography, ammonium sulfate precipitation, gel filtration and ion exchange chromatography. The enzyme appeared to be monomeric with subunit molecular weight of 43 kDa and isoelectric point of 4.85. The enzyme showed specificity for adenosine and exhibited Michaelis–Menten Kinetics with ▪ cat of 1112.41 min −1 and K m of 14.7 μM at pH 7.5. The pH and temperature optima for enzyme activity were 7–7.5 and 25 °C, respectively. Free energy (Δ G ∗), enthalpy (Δ H ∗) and entropy (Δ S ∗) of activation for denaturation of adenosine deaminase at 50 °C were 88.94, 99.65 kJ mol −1 and 33.16 J mol −1, respectively. The purified enzyme had half-lives of 636 and 61 min at 25 and 50 °C, respectively. The activation energy for catalysis of camel skeletal muscle adenosine deaminase was 9.13 kJ mol −1. Free energy (Δ G #), enthalpy (Δ H #) and entropy (Δ S #) of activation for hydrolysis of adenosine deaminase at 25 °C were 50.35, 6.65 kJ mol −1 and −146.62 J mol −1, respectively. Purine riboside inhibited the enzyme competitively with K i of 16 μM.