Purifi cation of a Toxic Metalloprotease Produced by the Pathogenic Photobacterium damselae subsp. piscicida Isolated from Cobia (Rachycentron canadum)
2014
Liu, Bingzhong | Chuang, Wen-Hsiao | Lee, Kuo-Kau
The aim of the present study was to purify and characterize a toxic protease secreted by the pathogenic Photobacterium damselae subsp. piscicida strain CP1 originally isolated from diseased cobia (Rachycentron canadum). The toxin isolated by anion exchange chromatography, was a metalloprotease, inhibited by L-cysteine, ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(β-aminoethyl ether)N,N,N’,N’-tetraacetic acid (EGTA), 1,10-phenanthroline, N-tosyl-L-phenylalanine-chloromethyl ketone (TPCK), and N-α-ptosyl- L-lysine-chloromethyl ketone (TLCK), and showed maximal activity at pH 6.0 - 8.0 and an apparent molecular mass of about 34.3 kDa. The toxin was also completely inhibited by HgCl₂, and partially by sodium dodecyl sulfate (SDS) and CuCl₂. The extracellular products and the partially purified protease were lethal to cobia with LD₅₀ values of 1.26 and 6.8 μg protein/g body weight, respectively. The addition of EDTA completely inhibited the lethal toxicity of the purified protease, indicating that this metalloprotease was a lethal toxin produced by the bacterium.
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