Abstract
Direct studies of the amino acid sequence of an E. coli plasmid-coded penicillinase (penicillin amido-.beta.-lactamhydrolase, EC 3.5.2.6) are in complete agreement with results derived from the translation of the DNA sequence of a related plasmid, apart from a single amino acid substitution. This penicillinase from a gram-negative bacterium shows 30-35% identity with functionally similar enzymes from gram-positve bacteria.