Beta-Lactamase is an enzyme which catalyzes the hydrolysis of the beta
-lactam ring of penicillins and cephalosporins. By similarity analysis
of amino acid sequences in a database, the amino acid sequence deduce
d from the nucleotide sequence of the upstream region of cytochrome c
oxidase subunit II from Paracoccus denitrificans was found to have an
unusually high score of homology to that of a portion of beta-lactamas
es from Gram-negative bacteria. Furthermore, the nucleotide sequences
corresponding only to this region had a very high score of similarity
among them. The phylogenetic tree constructed on the basis of the amin
o acid sequences was in accord with that constituted on the 5S rRNA's.
Moreover, the molar G + C contents and the codon usage were similar t
o those in their respective bacteria. It is suggested, therefore, that
the nucleotide sequence in P. denitrificans was positioned by a trans
fer of a part of a beta-lactamase gene formed as a result of gene dupl
ication or it was formed by a deletion of the essential region of the
beta-lactamase gene, although no beta-lactamase gene has been yet dete
cted in P. denitrificans.