A method of restoring activity in phenylalanine hydroxylase is provided. The method comprises exposing the phenylalanine hydroxylase to shikimic acid, a functionally equivalent analogue thereof, a pharmaceutically acceptable salt of shikimic acid or analogue thereof, or combinations thereof, A method of screening for allosteric activators for a target enzyme is also provided comprising the steps of: denaturing the target enzyme with a first chaotropic agent to yield denatured enzyme, incubating the denatured enzyme with a candidate compound under denaturing conditions to allow enzyme refolding, and assaying enzyme activity in the presence of enzyme substrate and a candidate compound； and if enzyme activity of the denatured enzyme was restored in step i) by at least about 10% of residual enzyme activity, denaturing the target enzyme with a second chaotropic agent to yield denatured enzyme, incubating the denatured enzyme with the candidate compound under non-denaturing conditions to allow enzyme refolding, and assaying enzyme activity in the presence of enzyme substrate and the candidate compound, wherein an increase in enzyme activity of at least about 10% of residual enzyme activity indicates that the candidate compound is an allosteric activator of the target enzyme.
