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

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.

Crystallization and preliminary X-ray investigation of holotryptophanases from Escherichia coli and Proteus vulgaris.

Crystals of Proteus vulgaris holotryptophanase have been grown by the hanging-drop technique using polyethylene glycol 4000 as precipitant in the presence of monovalent cations K+ or Cs+. Orthorhombic crystals (P2(1)2(1)2(1)) grown with Cs+ have unit cell parameters a = 115.0 A, b = 118.

New crystal form of cytosolic chicken aspartate aminotransferase suitable for high-resolution X-ray analysis.

Four new crystal forms of chicken cytosolic aspartate aminotransferase have been grown from polyethylene glycol solutions. Crystals of the unliganded enzyme and of enzyme liganded with maleate diffract to 1.8 A resolution.