• l-amino-acid ligases;
  • dipeptides;
  • substrate specificity

l-Amino-acid ligases (LALs) are enzymes which catalyze the formation of dipeptides by linking two l-amino acids. Although many dipeptides are known and expected to have medical and nutritional benefits, their practical use has been limited owing to their low availability and high expense. LALs are potentially desirable tools for the efficient production of dipeptides; however, the molecular basis of substrate recognition by LAL has not yet been sufficiently elucidated for the design of ideal LALs for the desired dipeptides. This report presents the crystal structure of the LAL BL00235 derived from Bacillus licheniformis NBRC 12200 determined at 1.9 Å resolution using the multi-wavelength anomalous dispersion method. The overall structure of BL00235 is fairly similar to that of YwfE, the only LAL with a known structure, but the structure around the catalytic site contains some significant differences. Detailed structural comparison of BL00235 with YwfE sheds some light on the molecular basis of the substrate specificities.