STUDIES ON MUTANTS OF BACILLUS SUBTILIS REQUIRING D-GLUTAMIC ACID

To look for the site of genetic block in the mutants of Bacillus subtilis K requring D-glutamic acid, several enzymes that were considered important for the biosynthesis of D- and L-glutamic acid were investigated. In mutant 3d, alanine racemase activity was about one tenth of that in the wild-type strain. It appears therefore that the block site in this mutant is between L-alanine and D-alanine. The mutant requires D-alanine, D-aspartic acid, or D-glutamic acid for growth.L-Alanine dehydrogenase activity was exceptionally low in mutant 2a. Because the mutant is able to synthesize L-aspartic acid and L-glutamic acid from fumarate too, the requirement of L-alanine, D-alanine, D-aspartic acid, or D-glutamic acid may be due to the slow reaction between pyruvate and L-alanine.Mutant 4a possesses a low activity of D-alanine-D-glutamic acid transaminase and responds to L-aspartic acid, L-glutamic acid, D-aspartic acid, or D-glutamic acid. The dependency on D-aspartic acid or D-glutamic acid is reasonable if these D-amino acids are produced from D-alanine by transamination, while the dependency on L-aspartic acid or L-glutamic acid remains unexplained. The correlation between a genetic damage and an enzyme formation was discussed in this connection.