The Subunit Structure of the Aliphatic Amidase from Pseudomonas aeruginosa

The molecular weight of Pseudomonas aeruginosa amidase was found to be 200000 by sedimentation equilibrium analysis; the sedimentation coefficient was 10.6 S. The subunit molecular weight determined by electrophoresis in dodecylsulphate‐acrylamide gels and gel filtration on Sephadex G‐200 in dodecylsulphate‐p‐chloromercuribenzoate solution was 33000—35000. The amino acid composition of the enzyme was determined. Only one N‐terminal amino acid, methionine, and one C‐terminal amino acid, alanine, were found indicating that the subunits were identical. Further evidence for a structure comprising 6 identical subunits came from both tryptic fingerprints and reaction of the enzyme with the cross‐linking reagent dimethyl suberimidate.