Wechselwirkungen der Hefe-Phosphofructokinase mit Dextranblau 2000

Yeast phosphofructokinase binds to Blue Dextran 2000® with remarkable high affinity. Whereas phosphofructokinase from muscle and erythrocytes also have high affinity to Blue Dextran, aldolase, hexokinase, pyruvate kinase from muscle and glyceraldehyde-3-phosphate dehydrogenase show no affinity to this chromophore. The chromophoric component of Blue Dextran seems to be responsible for these interactions, because chromophore-free dextran 2000 does not show any affinity to phosphofructokinases. Blue Dextran immobilized by fixation in cross-linked polyacrylamide gel can be used as a valuable tool for affinity chromatography of phosphofructokinase. The conditions of binding, namely pH dependence, effects of ionic strength and of enzyme effectors have been studied using gel-fixed phosphofructokinase. ATP (2–3 mM) but not ITP (up to 5 mM) specifically splits the enzyme chromophore complex. With non-inhibitory concentrations of ATP Blue Dextran inhibits the enzyme very strongly showing competition with respect to ATP. No correlation between inhibition by Blue Dextran and fructose-6-phosphate concentration could be detected. A model is proposed for the interactions of Blue Dextran with phosphofructokinase, postulating binding of the chromophore to the ATP binding sites of the enzyme.