Occurrence of D-amino acids in some natural materials.

Although the naturally occurring or-amino acids are usually of the L configuration, examples continue to accumulate of the occurrence in natural products of n-amino acids (1). Certainly the most surprising reports of this type have been those of Kogl and coworkers on the isolation of n-glutamic acid from cancerous tissue. Since his original publication in 1939 (2), and despite the fact that his findings have not been confirmed in other laboratories (3), Kiigl has repeatedly reaffirmed his original contention and reinforced it with additional experimental data (4). The recent studies of antibiotics have provided notable and indisputable instances of the occurrence of n-amino acids in natural products. Even the penicillins yield on acid hydrolysis an amino acid (penicillamine) of n configuration. In the course of a study of the amino acid metabolism of penicillinproducing molds, it seemed of interest to examine the mold materials for the presence of n-amino acids and to compare the results with those from some other antibiotic-producing organisms. Since this study was begun, Konikova and Dobbert (5) have reported the presence of large quantities of n-amino acids in hydrolysates of Bacillus brtis, Dunn et al. (6) have found evidence for n-glutamic acid in hydrolysates of Lactobacillus arabi~ZOSUS, and Holden and Snell (7) have clearly demonstrated the presence of n-alanine in the latter organism and in some other lactobacilli.