Isolation of DD Carboxypeptidase from Streptomyces albus G Culture Filtrates

Streptomyces albus G secretes a soluble DD carboxypeptidase whose catalytic activities are similar to those of the particulate DD carboxypeptidase from Escherichia coli. Both enzymes hydrolyze the C-terminal D-alanyl-D-alanine linkage of UDP-N-acetylmuramyl-L-alanyl-γ-D-glutamyl-(L)-meso-diaminopimelyl-(L)-D-alanyl-D-alanine and the enzyme-peptide interactions have identical Michaelis constants. Like the E. coli enzyme, the Streptomyces DD carboxypeptidase exhibits endopeptidase activities. The Streptomyces enzyme is lytic for those walls in which the peptidoglycan interpeptide bonds are mediated through C-terminal D-alanyl-D linkages. There is no strict requirement for a specific structure of the C-terminal D-amino acid residue. The tripeptide N°N^∈-bisacetyl-L-lysyl-D-alanyl-D-alanine is an excellent substrate for the Streptomyces DD carboxypeptidase.