Lysobacter enzymogenes produces an inducible p-lactamase and induction with 100 pg ampicillin ml-' resulted in an increase of more than 100-fold in enzyme activity. Various other p-lactam antibiotics also served as effective inducers. The enzyme was obtained from cells by osmotic shocking to release periplasmic components and it was purified primarily by ion-exchange chromatography and PAGE. The p-lactamase consists of one polypeptide with a molecular mass of about 28 kDa and an isoelectric point greater than 9.6. It is strongly inhibited by pchloromercuribenzoate and clavnlanic acid but not by EDTA. The enzyme readily hydrolyses several penicillins and cephalosporins, but not oxacillin or cloxacillin. The enzyme therefore belongs to group 2b of the bacterial 6-lactamases.

The gene for the periplasmic 19-lactamase of Lysobactev enzymogenes was isolated as part of a 1017 bp EcoRI fragment and the nucleotide sequence of the gene was determined. It has a G + C content of 71-5 % and encodes a 27 amino acid signal sequence and the mature /?-lactamase of 276 amino acids which has a mass of 29146 Da. The enzyme appears to be unique to L. enzymogenes but its amino acid sequence shows a high degree of homology with the amino acid sequences of the lactamase from Citvobactev diversus and other Class A 19-lactamases. The /?-lactamase gene of L. enzymogenes was expressed in Eschevichia coli using pUC118 as the vector. The production of active /?-lactamase was highest after the active growth phase of the expression host and reached levels which were about three times higher than those obtained with L. enzymogenes.