Purification of N-Acetylmuramic Acid-l-Alanine Amidase from Bacillus megaterium

The purification of the N-acetylmuramic acid l-alanine amidase from Bacillus megaterium KM is described. The enzyme has a molecular weight of 20,000 by sucrose density centrifugation and by acrylamide gel electrophoresis in sodium dodecyl sulfate. The isoelectric point is 8.2. The enzyme has a pH optimum of 6.8 and a sharp ionic strength optimum at Γ/2 = 0.02. The enzyme has a 4- to 10-fold higher initial velocity with cell walls obtained from logarithmically growing cells than from cell walls obtained from cells in stationary phase of growth. This difference in hydrolysis rate may account, in part, for the difference in cell wall turnover previously observed between stationary and logarithmic cells.