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prbA, a Gene Coding for an Esterase Hydrolyzing Parabens in Enterobacter cloacae and Enterobacter gergoviae Strains. Nelly Valkova, 2002.The new gene prbA encodes an esterase responsible for the hydrolysis of the ester bond of parabens in Enterobacter cloacae strain EM . This gene is located on the chromosome of strain EM and was cloned by several PCR approaches . The prbA gene codes for an immature protein of 533 amino acids, the first 31 of which represent a proposed signal peptide yielding a mature protein of a putative molecular mass of 54.6 kDa . This enzyme presents analogies with other type B carboxylesterases, mainly of eukaryotic origin . The cloning and expression of the prbA gene in a strain of Escherichia coli previously unable to hydrolyze parabens resulted in the acquisition of a hydrolytic capacity comparable to the original activity of strain EM, along with an increased resistance of the transformed strain to methyl paraben . The presence of homologues of prbA was tested in additional ubiquitous bacteria, which may be causative factors in opportunistic infections, including Enterobacter gergoviae, Enterobacter aerogenes, Pseudomonas agglomerans, E . coli, Pseudomonas aeruginosa, and Burkholderia cepacia . Among the 41 total strains tested, 2 strains of E . gergoviae and 1 strain of Burkholderia cepacia were able to degrade almost completely 800 mg of methyl paraben liter-1 . Two strains of E . gergoviae, named G1 and G12, contained a gene that showed high homology to the prbA gene of E . cloacae and demonstrated comparable paraben esterase activities . The significant geographical distance between the locations of the isolated E . cloacae and E . gergoviae strains suggests the possibility of an efficient transfer mechanism of the prbA gene, conferring additional resistance to parabens in ubiquitous bacteria that represent a common source of opportunistic infections . Characterization of Chitinase Genes from an Alkaliphilic Actinomycete, Nocardiopsis prasina OPC-131. Hiroshi Tsujibo, 2003.An alkaliphilic actinomycete, Nocardiopsis prasina OPC-131, secretes chitinases, ChiA, ChiB, and ChiB  , in the presence of chitin . The genes encoding ChiA and ChiB were cloned and sequenced . The open reading frame (ORF) of chiA encoded a protein of 336 amino acids with a calculated molecular mass of 35,257 Da . ChiA consisted of only a catalytic domain and showed a significant homology with family 18 chitinases . The chiB ORF encoded a protein of 296 amino acids with a calculated molecular mass of 31,500 Da . ChiB is a modular enzyme consisting of a chitin-binding domain type 3 (ChtBD type 3) and a catalytic domain . The catalytic domain of ChiB showed significant similarity to Streptomyces family 19 chitinases . ChiB was the truncated form of ChiB lacking ChtBD type 3 . Expression plasmids coding for ChiA, ChiB, and ChiB were constructed to investigate the biochemical properties of these recombinant proteins . These enzymes showed pHs and temperature optima similar to those of native enzymes . ChiB showed more efficient hydrolysis of chitin and stronger antifungal activity than ChiB, indicating that the ChtBD type 3 of ChiB plays an important role in the efficient hydrolysis of chitin and in antifungal activity . Furthermore, the finding of family 19 chitinase in N. prasina OPC-131 suggests that family 19 chitinases are distributed widely in actinomycetes other than the genus Streptomyces .
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