Synergistic effect of AMP and fructose 2,6-bisphosphate on the protection of fructose 1,6-bisphosphatase against inactivation by trypsin.

The rate of inactivation of chicken liver fructose 1,6-bisphosphatase by trypsin is reduced if the digestive reaction is conducted in the presence of AMP or fructose 2,6-bisphosphate. The effects of these 2 compounds are synergistic. Although fructose 1,6-bisphosphate does not protect the enzyme against tryptic inactivation, it can enhance the effect of AMP. Selective modification of the AMP allosteric site of fructose 1,6-bisphosphatase with pyridoxal-P and NaBH4 renders the enzyme more resistant to tryptic inactivation, but the modified enzyme is no longer responsive to the protective effect of AMP.