Crystal structure and mechanistic implications of N2-(2-carboxyethyl)arginine synthase, the first enzyme in the clavulanic acid biosynthesis pathway.
Article Details
- CitationCopy to clipboard
Caines ME, Elkins JM, Hewitson KS, Schofield CJ
Crystal structure and mechanistic implications of N2-(2-carboxyethyl)arginine synthase, the first enzyme in the clavulanic acid biosynthesis pathway.
J Biol Chem. 2004 Feb 13;279(7):5685-92. Epub 2003 Nov 17.
- PubMed ID
- 14623876 [ View in PubMed]
- Abstract
The initial step in the biosynthesis of the clinically important beta-lactamase inhibitor clavulanic acid involves condensation of two primary metabolites, D-glyceraldehyde 3-phosphate and L-arginine, to give N2-(2-carboxyethyl)arginine, a beta-amino acid. This unusual N-C bond forming reaction is catalyzed by the thiamin diphosphate (ThP2)-dependent enzyme N2-(2-carboxyethyl)arginine synthase. Here we report the crystal structure of N2-(2-carboxyethyl)arginine synthase, complexed with ThP2 and Mg2+, to 2.35-A resolution. The structure was solved in two space groups, P2(1)2(1)2(1) and P2(1)2(1)2. In both, the enzyme is observed in a tetrameric form, composed of a dimer of two more tightly associated dimers, consistent with both mass spectrometric and gel filtration chromatography studies. Both ThP2 and Mg2+ cofactors are present at the active site, with ThP2 in a "V" conformation as in related enzymes. A sulfate anion is observed in the active site of the enzyme in a location proposed as a binding site for the phosphate group of the d-glyceraldehyde 3-phosphate substrate. The mechanistic implications of the active site arrangement are discussed, including the potential role of the aminopyrimidine ring of the ThP2. The structure will form a basis for future mechanistic and structural studies, as well as engineering aimed at production of alternative beta-amino acids.