5ll2

Publication Abstract from PubMed

The isoleucine 2-epimerase from Lactobacillus buchneri has been previously identified and characterized to catalyze the pyridoxal 5'-phosphate (PLP)-dependent racemization and epimerization of a broad spectrum of nonpolar amino acids from L- to D-form and vice versa, in particular isoleucine. In this study, crystal structures of both native and PLP-complex forms of this racemase are presented at 2.6 and 2.15 A resolution, respectively. Both structures show that the protein belongs to the fold-type I subgroup of PLP-dependent enzymes and is very close to aminobutyrate aminotransferases family, as it has been suspected because of their sequence homology. The extensive structural comparison with fold-type I enzymes with known amino acid racemization activities, including the alpha-amino-epsilon-caprolactam racemase from Achromobacter obae and the cystathionine beta-lyase from Escherichia coli, allows us to identify the active site residues responsible for its nonpolar amino acid recognition and reactivity specificity. Our observations also suggest that the racemization reaction by the fold-type I racemases may generally occur thanks to a revised two-base mechanism. Lastly, both structures reveal details on the conformational changes provoked by PLP binding that suggest an induced fit of the active site "entrance door", necessary to accommodate PLP and substrate molecules.

Structural insights into the substrate recognition and reaction specificity of the PLP-dependent fold-type I isoleucine 2-epimerase from Lactobacillus buchneri.,Awad R, Gans P, Reiser JB Biochimie. 2017 Mar 23. pii: S0300-9084(16)30277-2. doi:, 10.1016/j.biochi.2017.03.015. PMID:28344038^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.