A method of affecting a multimeric protein comprising an equilibrium of assembly states, each assembly having a plurality of units, wherein each of the units comprises a first complementary surface and a second complementary surface and wherein the first complementary surface of one unit is associated with the second complementary surface of another unit, provided that the assembly is at least one of different quaternary isoforms under four conditions, wherein the method comprising: applying to the multimeric protein a composition comprising a compound adapted to affect formation of an active form of the multimeric protein associating the composition with an active form of the multimeric protein and promoting the multimeric protein to assemble into the active form, thereby affecting the multimeric protein to form the active form, wherein the multimeric protein is phenylalanine hydroxylase.
