Glucokinase of pea seeds

1. Glucokinase (ATP : D-glucose 6-phosphotransferase, EC 2.7.1.2) was extracted from pea seeds and purified by fractionation with (NH4)2SO4 and chromatography on DEAE-cellulose and Sephadex. 2. The relative rates of phosphorylation of glucose, mannose and fructose (final concentration 5 mM) were 100, 64 and 11. 3. The Km for glucose of pea-seed glucokinase was 70 muM and the Km for mannose was 0.5 mM. The Km for fructose was much higher (30 mM). 4. Mg2+ ions were essential for activity. Mn2+ could partially replace Mg2+. 5. Enzyme activity was not inhibited by glucose 6-phosphate. A number of other metabolites had no effect on glucokinase activity. 6. Pea-seed glucokinase was inhibited by relatively low concentrations of ADP.