Effect of disruption by sonication under different conditions on the activity of glucose dehydrogenase from resting spores of Bacillus subtilis.

The activity of glucose dehydrogenase present in resting spores of Bacillus subtilis varied strikingly with the conditions for disrupting the spores by sonic treatment, namely, the time and strength of sonication, and the type and pH of the solution used for suspending the spores. When the resting spores were sonicated for 30 min at a current of 1.45 A in 100 mM phosphate buffer in the range of pH 6.0 to 6.6 or in deionized water, the enzyme activity of the former suspension was approximately 10 times higher than that of the latter suspension. However, the enzyme activity of the latter was markedly stimulated in the presence of sodium chloride. The glucose dehydrogenase from resting spores disrupted in 100 mM phosphate buffer (pH 6.6) was a salt-independent, active enzyme with a molecular weight of about 120,000, whereas the enzyme from resting spores disrupted in deionized water was a salt-dependent, inactive one with a molecular weight of about 55,000. A high concentration of dipicolinic acid strongly inhibited activation by a salt of inactive glucose dehydrogenase from resting spores in deionized water, suggesting one of its several important roles in vivo.