L-Amino acid ligase (EC 6.3.2.28) is a microbial enzyme catalyzing formation of an alpha-peptide bond from unprotected
L-amino acids in an ATP-dependent manner. The YwfE protein from
Bacillus subtilis 168 was the first reported
L-amino acid ligase, and it synthesizes various dipeptides. Thereafter, several
L-amino acid ligases were newly obtained by
in silico analysis using the ATP-grasp motif. But these
L-amino acid ligases synthesize only dipeptide and no longer peptide. A novel
L-amino acid ligase capable of catalyzing oligopeptide synthesis is required to increase the variety of peptides. We have previously found a new member of
L-amino acid ligase, RizA, from
B. subtilis NBRC3134, a microorganism that produces the peptide-antibiotic rhizocticin. We newly found that a gene at approximately 9 kbp upstream of rizA encoded a novel
L-amino acid ligase RizB. Recombinant RizB synthesized homo-oligomers of branched-chain amino acids consisting of 2 to 5 amino acids, and also synthesized various heteropeptides. RizB is the first reported
L-amino acid ligase that catalyzes oligopeptide synthesis. In addition, we obtained
L-amino acid ligases showing oligopeptide synthesis activities by
in silico analysis using BLAST, which is a set of similarity search programs. These
L-amino acid ligases showed low similarity in amino acid sequence, but commonly used branched-chain amino acids, such as RizB, as substrates. Furthermore, the spr0969 protein of
Streptococcus pneumoniae synthesized longer peptides than those synthesized by RizB, and the BAD_1200 protein of
Bifidobacteria adolescentis showed higher activity toward aromatic amino acids than toward branched-chain ones.
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