A leucylglycine-splitting enzyme from E. coli ribosomes has been purified and its properties studied. The ribosomal proteins were solubilized by disrupting the ribosomal particles in 1 M Tris. As purification proceeded the ionic strength required to keep the proteins in solution steadily decreased until, in the later stages, the enzyme could be fractionated on ion-exchange columns at low ionic strengths. The ribosomal peptidase requires K+ or Cs+ and Mn2+ or Mg2+ for full activity and is inhibited by Na+ and Li+. It is completely inhibited by EDTA. The enzyme, which is a basic protein with no absorbancy maximum in the 280 mμ region of the spectrum, has a broad optimum pH range from 7.5 to 9.2. On small-scale preparations over a 1000-fold purification has been obtained.
Purification and Properties of Dipeptidase M from Escherichia coli B