Abstract
(1) D-Alanyl-D-alanine, D-alanine, L-alanine, D, L-α-aminobutyric acid, D-serine, and L-methionine were found to reverse the action of O-carbamyl-D-serine on Bacillus subtilis in synthetic medium. (2) When O-carbamyl-D-serine was added to the growth medium a relative increase of L-aianine and ammonia, and an accumulation of a nucleotide peptide were observed. The structure of the nucleotide peptide was identified as UDP-MurNAc-Ala-Glu-DAP. (3) Several compounds related to O-carbamyl-D-serine were synthesized and tested for their antimicrobial activity. Only O-carbamyl-D-serine methyl ester exhibited activity, which could be reversed by D-alanyl-D-alanine, D-alanine and L-alanine. N-D-Alanyl-O-carbamyl-D-serine which has been reported to be enzymatically synthesized by D-alanyl-D-alanine synthetase of Streptococcus faecalis R, did not have antimicrobial activity. (4) We concluded that the primary site of the action of O-carbamyl-D-serine in Bacillus subtilis is an enzymatic system controlling racemization of alanine. A similar conclusion was previously reached by LYNCH and NEUHAUS by use of enzymatic methods in Streptococcus faecalis R.
