Isolation of Pure Hexokinase from Yeast

has been obtained in pure form from baker 's yeast by a method based chiefly on fractional precipitation with alcohol. 1 mg. of the pure protein catalyzes the transfer of 4.2 mg. P per minute at 30 ° and pH 7.5. The reported crystallization of the protein from dilute alcohol is not readily reproducible. Crystallization from ammonium sulfate (Fig. 1) according to the procedure of Kunitz and McDonald does not change the specific activi ty of this material.