Purification and properties of human hexokinase

Preliminary attempts were made to isolate hexokinase from human erythrocytes and placenta. The final purifications were made from heart, which contained more enzyme than other tissues. From 1.15 kg of heart, 25 mg of hexokinase was obtained of specific activity 58 units/rng. This represents a 1,700-fold purification and a yield of I+7% over six steps. A critical development in isolating " this enzyme was the use of affinity chromatography, using glucosamine linked to Sepharose". The material contained"a single protein component according to electrophoresis on starch gel, cellulose acetate and polyacrylamide gel. It gave a single peak on gel filtration, and on sedimentation in the ultracentrifuge. However, a heterogeneity in size was indicated by electrophoresis on SDS-polyacrylamide gels which gave two bands of approximately equal intensity. The apparent molecular weights of these components were 109,000 and 124,000. The small difference in size has not resolved by the other techniques used. Gel filtration on Sephadex G-200 suggested a molecular weight-of 106,000, as did the combination of the 'sedimentation coefficient of 5.5 S and diffusion coefficient of 47 μm2/s.