Structures of apo- and holo-tyrosine phenol-lyase reveal a catalytically critical closed conformation and suggest a mechanism for activation by K+ ions.

ABSTRACT: Tyrosine phenol-lyase, a tetrameric pyridoxal 5'-phosphate dependent enzyme, catalyzes the reversible hydrolytic cleavage of L-tyrosine to phenol and ammonium pyruvate. Here we describe the crystal structure of the Citrobacter freundii holoenzyme at 1.9 A resolution. The structure reveals a network of protein interactions with the cofactor, pyridoxal 5'-phosphate, and details of coordination of the catalytically important K+ ion. We also present the structure of the apoenzyme at 1.85 A resolution. Both structures were determined using crystals grown at pH 8.0, which is close to the pH of the maximal enzymatic activity (8.2). Comparison of the apoenzyme structure with the one previously determined at pH 6.0 reveals significant differences. The data suggest that the decrease of the enzymatic

SUBMITTER: Milic D 

PROVIDER: S-EPMC2691550 | biostudies-literature | 2006 Jun

REPOSITORIES: biostudies-literature