X-ray Inactivation of Urease in Dilute Solution

Summary The inactivation of jack-bean urease has been measured in the following conditions: 50-500 µg/ml. in 0·05 M phosphate buffer, pH 7, 0°c, in the presence of air. The yield is 0·015 molecules/(100 eV). This value is low, but the weight of enzyme inactivated per unit dose, 7·4 × 10−11 g/erg, is similar to that found for many other enzymes. It is suggested that some functional groups in the urease molecule can react with radicals from the solvent without loss of the enzymatic activity. 'Repair reactions' may be taking place, which consume radicals without causing any permanent changes in the enzyme.