Summary α-Urease (mol wt 480,000) inactivated by titration to pH 11.3 has the same electrophoretic mobility as active α-urease. Titration to pH 11.6–11.9 results in partial dissociation to A1-urease (mol wt 240, 000) as judged by electrophoretic mobility equivalent to that of active A1-urease produced by glycol. At slightly higher pH (12.4), full denaturation of the enzyme occurs. The results are similar, quantitatively, to those produced by acid titration, and qualitatively to the dissociation produced by high ionic strengths near neutral pH. Charge separation is thus indicated as the mechanism.