Hydrogen Ion-induced Reversible Inactivation and Dissociation of Formyltetrahydrofolate Synthetase

Formyltetrahydrofolate synthetase undergoes inactivation at pH values below 7. Inactivation is accompanied by both the dissociation of the tetramer into monomers and the exposure of aromatic amino acids to the solvent. The rate of inactivation is a function of pH. This rate and the rate of exposure of tryptophan residues to the aqueous environment follow first order kinetics. After prolonged incubation under acidic conditions the monomers are still capable of reassociating to form tetramers but the tetramers produced have a reduced catalytic activity.