The crystal structure of the Pseudomonas dacunhae aspartate-beta-decarboxylase dodecamer reveals an unknown oligomeric assembly for a pyridoxal-5'-phosphate-dependent enzyme.

The Pseudomonas dacunhael-aspartate-beta-decarboxylase (ABDC, aspartate 4-decarboxylase, aspartate 4-carboxylyase, E.C. 4.

Role of lysine-256 in Citrobacter freundii tyrosine phenol-lyase in monovalent cation activation.

Tyrosine phenol-lyase (TPL) from Citrobacter freundii is dependent on monovalent cations, K(+) or NH(4)(+), for high activity. We have shown previously that Glu-69, which is a ligand to the bound cation, is important in monovalent cation binding and activation [Sundararaju, B., Chen, H.

Threonine-124 and phenylalanine-448 in Citrobacter freundii tyrosine phenol-lyase are necessary for activity with L-tyrosine.

Thr-124 and Phe-448 are located in the active site of Citrobacter freundii tyrosine phenol-lyase (TPL) near the phenol ring of a bound substrate analogue, 3-(4'-hydroxyphenyl)propionic acid [Sundararaju, Antson, Phillips, Demidkina, Barbolina, Gollnick, Dodson and Wilson (1997) Biochemistry 36, 6502-6510]. Thr-124 is replaced by Asp and Phe-448 is replaced by His in the crystal structure of a structurally similar enzyme, Proteus vulgaris tryptophan indole-lyase, which has 50% identical residues. Hence, Thr-124 and Phe-448 in TPL were mutated to Ala or Asp, and His, respectively, in order to probe the role of these residues in the reaction specificity for L-Tyr.