The characterization of an alanine racemase mutant ofEscherichia coli

SUMMARY Among temperature-sensitive mutants of Escherichia coli a strain was discovered requiring D-alanine for growth. It was proved to possess an altered alanine racemase. The structural gene for this enzyme, designated alr , is located between metB and pur A . The properties of the enzyme and its locus suggest that it is not under control of the mechanisms which regulate mucopeptide formation. A suppressor of the alr mutation was discovered near trp , and termed msuA .