Simultaneous purification and characterization of glucokinase, fructokinase and glucose-6-phosphate dehydrogenase from Zymomonas mobilis

Abstract

The three enzymes glucokinase (EC 2.7.1.2), fructokinase (EC 2.7.1.4) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) were isolated in high yield from extracts of Zymomonas mobilis. The principal steps in the isolation procedures involved the use of selected dye-ligand adsorbent columns, with affinity elution of two of the three enzymes. Glucokinase and fructokinase are dimeric proteins (2 × 33000 Da and 2 × 28000 Da respectively) and glucose-6-phosphate dehydrogenase is a tetramer (4 × 52000 Da). Some similarities in the structural and kinetic parameters of the two kinases were noted, but they have absolute specificity for their substrates. Fructokinase is strongly inhibited by glucose; otherwise non-substrate sugars had little effect on any of the three enzymes.