Localization of the Potassium Ion Activation Site in Human Liver Fructose 1,6-Bisphosphatase

Three mouse monoclonal antibodies of human liver fructose 1,6-bisphosphatase are shown to bind to the enzyme at different sites as determined by ELISA. The binding of one of the monoclonal antibodies, L2E1, mimics the effects of K + ions, including increase in the enzyme activity and enhancement of the sensitivity of the enzyme to AMP inhibition. We tentatively suggest that human liver FruP 2ase may have a specific K + activation site, which at least partially overlaps with the L2E1 binding region. This site has been localized by analyzing the peptide fragments formed by cleavage with cyanogen bromide.