Occurrence of peptidyl D-amino acids in soluble fractions of several eubacteria, archaea and eukaryotes

摘要

The occurrence of peptidyl D-amino acids in the aqueous soluble fractions was investigated in various eubacteria, some archaea and some eukaryotes. The contents of the D-enantiomers of serine, alanine, proline, glutamate (glutamine), aspartate (asparagine) and phenylalanine were determined with cell- and tissue-extracts, by means of acid hydrolysis and high-performance liquid chromatography. The rate of D-enantiomer (%, the ratio in molar concentration of a D-amino acid to the total of the D-amino acid and the corresponding L-amino acid) of alanine and glutamate were high in some Gram-positive eubacteria: 11.7% in Staphylococcus epidermidis and 10.3% in Streptococcus pyogenes for alanine, and 22.3% for glutamate in Bacillus YN-1. The D-glutamate content was also high (8.0%) in the Gram-negative eubacterium, Thiobacillus ferrooxidans. D-Aspartate was common, as was D-glutamate: the highest D-aspartate content was detected in an archaeum, Pyrobaculum islandicum (4.0%). However, the content of D-aspartate was low, 0.2-1.8% in most other bacteria. The presence of D-serine was shown in some organisms, but that of D-proline was scarce. The D-enantiomer of phenylalanine was not detected in any of the organisms examined. These results indicate that of the bacteria examined herein most Gram-negative and some Gram-positive eubacteria, as well as archaea contain only low levels of D-amino acids in the soluble peptidyl fraction, and the levels were comparable to those in eukaryotes examined. To our knowledge, the general presence of peptidyl fraction, and the levels were comparable to those in eukaryotes examined. To our knowledge, the general presence of peptidyl D-amino acids in these organisms, especially archaea and eukaryotic cells including those from rat liver tissues, has been shown here for the first time.