Physicochemical and kinetic properties of iodinated yeast 3-phosphoglycerate kinase

Abstract

There apparently is a critical tyrosyl residue in yeast 3-phosphoglycerate kinase. The iodination of this enzyme resulted in an inactivation following 1st-order kinetics. The extent of the modification was limited to only 1 tyrosyl residue. The monoiodotyrosine formation which led to inactivation of the enzyme did not induce any significant conformational change as evidenced by H exchange and optical rotatory dispersion. The role of this tyrosine in the action of the yeast 3-phosphoglycerate kinase was studied. An effective protection against inactivation was observed with 3-phosphoglycerate, and the characteristic spectral effect of 3-phosphoglycerate binding could not be detected in the modified enzyme. The essential tyrosyl residue may play a role in substrate binding.