Mutating the tight-dimer interface of dihydrodipicolinate synthase disrupts the enzyme quaternary structure: Toward a monomeric enzyme

Abstract

Dihydrodipicolinate synthase (DHDPS) is a tetrameric enzyme that is the first enzyme unique to the (S)-lysine biosynthetic pathway in plants and bacteria. Previous studies have looked at the important role of Tyr107, an amino acid residue located at the tight-dimer interface between two monomers, in participating in a catalytic triad of residues during catalysis. In this study, we examine the importance of this residue in determining the quaternary structure of the DHDPS enzyme. The Tyr107 residue was mutated to tryptophan, and structural, biophysical, and kinetic studies were carried out on the mutant enzyme. These revealed that while the solid-state structure of the mutant enzyme was large..