glucose dehydrogenase isoenzymes are stabilized in presence of 2 M NaCl. The effect is especially large for GlcDH-III, which is the most unstable enzyme
purified enzyme is indefinitely stable in the frozen state or in solution at pH 6.5 containing 3 M NaCl and a protein concentration of more than 0.5 mg/ml. Diluted enzyme solutions can be stabilized to the same degree by adding 0.5% polyvinylpyrrolidone. Any reduction of the ionic strength of enzyme solution leads to an irreversible inactivation which can be only partially prevented by additrion of polyvinylpyrrolidone
unstable at low ionic strength, in 67 mM phosphate buffer enzyme activity decreases to 80% within 5 hours at pH 6.5 and 0.01 mg/ml protein, reduction to 57% at 40 mM phosphate, high concentration of NAD inhibit dissociation