A beta-lactamase (EC 3.5.2.6 penicillinase, penicillin amino beta-lact
am-hydrolase) was purified from Shigella flexneri USCF-129 by an effic
ient two-stage procedure involving chromatography in Sephadex G-75 and
HPLC on a C-18-reverse phase column. The homogeneity of the purified
enzyme was confirmed by capillary zone electrophoresis (CZE), HPLC ele
ctrospray mass spectrometry (LC-ESMS) and amino acid sequence analyses
. The highly purified enzyme was a monomeric protein with a molecular
mass of 28.903 +/- 2 Da, as determined by LC-ESMS. The amino acid sequ
ence of the first 49 N-terminal residues of this beta-lactamase reveal
ed 100% similarity with the mature forms of the plasmid coded Escheric
hia coli enzymes (plasmid pBR 322 and R6K) a TEM-type beta-lactamase.