Purification, stability and kinetic properties of highly purified adenosine deaminase from Bacillus cereus NCIB 8122

Adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) from Bacillus cereus NCIB 8122 has been purified to electrophoretic homogeneity by ammonium sulfate precipitation, gel filtration through Sephadex G-100, DEAE-Sephadex A-50 chromatography and ion-exchange HPLC on DEAE-Polyol. The enzyme activity is stabilized (at temperatures from 0 degrees C to 40 degrees C) by 50 mM NH4+ or K+, while it is irreversibly lost in the absence of these or a few other monovalent cations. Glycerol (24% by volume) helps the cation in stabilizing the enzyme activity above 40 degrees C, but also exerts per se a noticeable protecting effect at room temperature. B. cereus adenosine deaminase displays the following properties: Mr on Sephadex G-200, 68,000; Mr in SDS-polyacrylamide gel electrophoresis, 53,700; optimal pH-stability (in the presence of 50 mM KCl) over the range 8-11 at 4 degrees C, and maximal catalytic activity at 30 degrees C between pH 7 and 10; Km for adenosine around 50 microM over the same pH range and Km for 2'-deoxyadenosine around 400 microM.