THE ASPARAGINE DEAMIDASE OF BACILLUS COAGULANS AND BACILLUS STEAROTHERMOPHILUS

Abstract

The purification and certain properties of L-asparagine deamidase of Bacillus coagulans and Bacillus stearothermophilus are described. Maximum enzyme activity was obtained at 55 °C. over a pH range of 7.5 to 8.5. The purified deamidase hyclrolyzed the L-isomer of asparagine quantitatively to aspartic acid and ammonia and did not attack the D-isomer. D-Asparagine inhibited the hydrolysis of the L-isomer. The Kmfor the inhibition reaction was found to be 1.87 × 10−2 M. The enzyme did not catalyze transamidation or hydroxylamine transfer reactions. Enzyme activity was inhibited by N-ethylmaleimide and p-chloromercuribenzoate. The inhibition by these agents was reversed by glutathione. In the absence of substrate the deamidase of both organisms was relatively heat labile at 55 °C. The heat lability of this enzyme is discussed in relation to the heat stability of other enzyme systems of thermophilic microorganisms.