D-Amino Acid Dipeptide Production Utilizing D-Alanine-D-Alanine Ligases with Novel Substrate Specificity

摘要

D-Alanine-D-alanine ligase (Ddl) is an important enzyme in the synthesis of bacterial peptido-glycan.The genes encoding Ddls from Escherichia coli K12 (EcDdlB),Oceanobacillus iheyensis JCM 11309 (OiDdl),Synechocystis sp.PCC 6803 (SsDdl) and Thermotoga maritima ATCC 43589 (TmDdl),the genomic DNA sequences of which have been determined,were cloned and the substrate specificities of these recombinant Ddls were investigated.Although OiDdl had a high substrate specificity for D-alanine;EcDdlB,SsDdl and TmDdl showed broad substrate specificities for D-serine,D-threonine,D-cysteine and glycine,in addition to D-alanine.Four D-amino acid di-peptides were produced using EcDdlB,and D-amino acid homo-dipeptides were successfully produced at high yields except for D-threonyl-D-threonine.