The production and molecular properties of the zinc β-lactamase of Pseudomonas maltophilia IID 1275

Abstract

The production and purification of a tetrameric Zn .beta.-lactamase from P. maltophilia IID 1275 were greatly improved. Three charge variants were isolated by chromatofocusing. The subunits each contain 2 atomic proportions of Zn and (in 2 type of the variants) 1 residue of cysteine. The thiol group is not, required for activity, nor does it appear to bind to the metal. Replacement of Zn by Co, Cd or Ni takes place at a measurable rate, and gives enzymes that are less active than the zinc enzyme. The properties of this enzyme differ from those of the other known Zn .beta.-lactamase, .beta.-lactamase II from Bacillus cereus. The amino acid sequence of the N-terminal 32 residues was determined; there is no similarity to the N-terminal sequences of other .beta.-lactamases.