Open AccessChromosomal beta-lactamase of Klebsiella oxytoca, a new class A enzyme that hydrolyzes broad-spectrum beta-lactam antibiotics
Author(s) -
Yoshichika Arakawa,
Michio Ohta,
Nobuo Kido,
Masashi Mori,
Hideo Ito,
Takayuki Komatsu,
Yasuaki Fujii,
Naoya Kato
Publication year - 1989
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.33.1.63
Subject(s) - klebsiella oxytoca , citrobacter freundii , beta lactamase , biology , nucleic acid sequence , peptide sequence , cephalosporin , microbiology and biotechnology , escherichia coli , gene , enterobacteriaceae , biochemistry , antibiotics
The chromosomally encoded beta-lactamase gene of Klebsiella oxytoca E23004, a strain resistant to cefoperazone and aztreonam, was cloned and expressed in Escherichia coli HB101. The molecular mass and pI of this enzyme were 28 kilodaltons and 7.4, respectively. Although the beta-lactamase of K. oxytoca hydrolyzed many cephalosporins, including broad-spectrum drugs, the nucleotide sequence and deduced amino acid sequence lacked homology with chromosomal class C beta-lactamase genes (ampC) of E. coli or Citrobacter freundii. Rather, about 45% nucleotide sequence homology and 40% deduced amino acid sequence homology were observed between the K. oxytoca beta-lactamase and TEM-1, a class A beta-lactamase which does not efficiently hydrolyze cephalosporins. Values of Km, relative Vmax, and relative Vmax/Km for the K. oxytoca beta-lactamase indicated that the enzyme is a penicillinase but that it can hydrolyze cefoperazone effectively and other broad-spectrum cephems weakly. Hence, the chromosomal beta-lactamase of K. oxytoca E23004 belongs to class A but differences in its amino acid sequence provide a broader spectrum of activity.