The Structure of l-Aspartate Ammonia-Lyase from Escherichia coli^,

Abstract

The X-ray crystal structure of l-aspartate ammonia-lyase has been determined to 2.8 A resolution. The enzyme contains three domains, and each domain is composed almost completely of alpha helices. The central domain is composed of five long helices. In the tetramer, these five helices form a 20-helix cluster. Such clusters have also been seen in delta-crystallin and in fumarase. The active site of aspartase has been located in a region that contains side chains from three different subunits. The structure of the apoenzyme has made it possible to identify some of the residues that are involved in binding the substrate. These residues have been examined by site-directed mutagenesis, and their putative roles have been assigned [Jayasekera, M. M. K., Shi, W., Farber, G. K., & Viola, R. E. (1997) Biochemistry 36, 9145-9150].

Substrate and Product Complexes of Escherichia coli Adenylosuccinate Lyase Provide New Insights into the Enzymatic Mechanism

“…[4][5][6][7][8][9] However, while the general structure of the ec-ADL protein is similar to those of the previously determined tm-and Pyrobaculum aerophilum (pa-) ADL enzymes, 7,32 significant conformational differences are observed between the proteins. A structural alignment of wild-type ec-ADL with monomers A of tmor pa-ADL yields rms deviations of 2.9 Å and 3.0 Å for all equivalent C α positions, respectively.…”

“…The structures of superfamily members has revealed that these enzymes are biologically active as homotetramers, with each monomer comprised of three distinct structural domains. [4][5][6][7][8][9] Although the overall sequence identity between the superfamily members is only ~15-30%, the enzymes are characterized by three regions of highly conserved amino acid residues (denoted C1-C3, respectively). Conserved region C3 contains the signature sequence 294 GSSxxPxKxN 303 (Escherichia coli ADL numbering).…”

L ‐Aspartase: New Tricks from an Old Enzyme

“…1). The interconversion between these enzyme forms is observed near neutral pH in both the maximum velocity ( V , ) and V,,,/K, pH profiles examined for the reaction in either direction 'The original amino acid numbering scheme has been increased by one since the publication of the high-resolution structure (Shi et al, 1997) to account for the N-terminal methionine that is present in the mature enzyme. (Karsten and Viola, 1991).…”

Use of Enzymes in the Synthesis of Amino Acids

“…YM55-1 [124]. On-going engineering projects will certainly benefit from the recently elucidated X-ray crystal structures of the E. coli aspartase [125] and of the thermostable aspartase from Bacillus sp. YM55-1 [126].…”