title: 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 43kDa and isoelectric point of 4.85. The enzyme showed specificity for adenosine and exhibited Michaelis-Menten Kinetics with kappa(cat) of 1112.41 min(-1) and K(m) of 14.7 microM at pH 7.5. The pH and temperature optima for enzyme activity were 7-7.5 and 25 degrees C, respectively. Free energy (DeltaG*), enthalpy (DeltaH*) and entropy (DeltaS*) of activation for denaturation of adenosine deaminase at 50 degrees C were 88.94, 99.65 kJmol(-1) and 33.16 Jmol(-1), respectively. The purified enzyme had half-lives of 636 and 61 min at 25 and 50 degrees C, respectively. The activation energy for catalysis of camel skeletal muscle adenosine deaminase was 9.13 kJmol(-1). Free energy (DeltaG#), enthalpy (DeltaH#) and entropy (DeltaS#) of activation for hydrolysis of adenosine deaminase at 25 degrees C were 50.35, 6.65 kJmol(-1) and -146.62 Jmol(-1), respectively. Purine riboside inhibited the enzyme competitively with K(i) of 16 microM.
authors.affiliation: Department of Biochemistry, College of Sciences, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia. srokayan@ksu.edu.sa
authors.forename: Salman
authors.initials: S
authors.lastname: Alrokayan
mesh_terms: D000243:Adenosine Deaminase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D000818:Animals; D002162:Camelus; D002384:Catalysis; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018482:Muscle, Skeletal / Q000201:enzymology*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000243:Adenosine Deaminase