The interaction of fructose 2,6-bisphosphate with an allosteric site of rat liver fructose 1,6-bisphosphatase

Rat liver fructose 1,6‐bisphosphatase can be protected against partial inactivation by N‐ethylmaleimide by low concentrations of fructose 2,6‐bisphosphate or high concentrations of fructose 1,6‐bisphosphate. The partially inactivated enzyme has a much reduced sensitivity to high substrate inhibition and has lost the sigmoid component of the inhibition by fructose 2,6‐bisphosphate; this compound is a simple linear competitive inhibitor of the modified enzyme. The results suggest that fructose 2,6‐bisphosphate can bind to the enzyme at two distinct sites, the catalytic site and an allosteric site. High levels of fructose 1,6‐bisphosphate probably inhibit by binding to the allosteric site