Binding of fructose-1,6-bisphosphate to yeast phosphofructokinase

Binding of fructose-1,6-bisphosphate to yeast phosphofructokinase (EC 2.7.1.11) was measured in a concentration range of 5 to 200 microM of fructose-1,6-bisphosphate with the ultrafiltration technique. At saturation two molecules of fructose-1,6-bisphosphate are bound per subunit of the octameric enzyme. Two distinct types of binding sites have been observed. The high affinity sites (KH = 32.7 +/- 5 microM) exhibit a hyperbolic response in respect to the binding of fructose-1,6-bisphosphate, the low affinity sites (KL = 57.2 +/- 6 microM) show significant positive cooperativity.