Purification and characterization of adenosine deaminase from camel skeletal muscle

Adenosine deaminase was purified (780-fold) from skeletal muscle of camel (Camelus Donnedarius) 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 isoclectric point of 4.85. The enzyme showed specificity for adenosine and exhibited Michaelis-Menten Kinetics with k(cat) of 1112.41 min(-1) and K-m of 14.7 muM at pH 7.5. The pH and temperature optima for enzyme activity were 7-7.5 and 25 degreesC, respectively. Free energy (DeltaG*), enthalpy (DeltaH*) and entropy (DeltaS*) of activation for denaturation of adenosine deaminase at 50 degreesC 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 degreesC, respectively. The activation energy for catalysis of camel skeletal muscle adenosine deaminase was 9.13 kJ mol(-1). Free energy (DeltaG(#)), enthalpy (DeltaH(#)) and entropy (DeltaS(#)) of activation for hydrolysis of adenosine deaminase at 25 degreesC 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 muM. (C) 2002 Elsevier Science Ltd. All rights reserved.