L-Amino acid ligase catalyzes dipeptide synthesis from unprotected L-amino acids in an ATP-dependent manner. We recently identified a new member of L-amino acid ligase, the plu1440 protein, from Photorhabdus luminescens subsp. laumondii TT01 by in silico analysis. This protein was found to synthesize dipeptides containing L-asparagine at the N-terminus, which is a novel substrate specificity. (C) 2009, The Society for Biotechnology, japan. All rights reserved.