Purification and properties of dipeptidase M from Escherichia coli B.

A peptidase from Escherichia coli B has been prepared in a highly pure form and characterized with respect to its substrate specificity, requirements for activity, size and subunit structure. This enzyme preferentially catalyzes the hydrolysis of certain methionyl dipeptides and for this reason is referred to as dipeptidase M. Of the substrates tested with the homogeneous enzyme methionylalanine and methionylserine were the most rapidily hydrolyzed. Other substrates were cleaved more slowly, if at all, by this peptidase. The substrate specificity of this enzyme suggests that it may be involved in the removal of NHz-terminal methionine from newly initiated E. coli proteins.