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

Abstract

The 3 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 Z. mobilis. The principal steps in the isolation procedures involved the use of selected dye-ligand adsorbent columns, with affinity elution of 2 of the 3 enzymes. Glucokinase and fructokinase are dimeric proteins (2 .times. 33,000 Da [daltons] and 2 .times. 28,000 Da, respectively) and glucose-6-phosphate dehydrogenase is a tetramer (4 .times. 52,000 Da). Some similarities in the structural and kinetic parameters of the 2 kinases were noted, but they had absolute specificity for their substrates. Fructokinase is strongly inhibited by glucose; otherwise nonsubstrate sugars had little effect on any of the 3 enzymes.