title: Purification and characterisation of an extracellular metalloprotease, serine protease and haemolysin of Aeromonas hydrophila strain B32: all are lethal for fish.
abstract: Three different lethal (for rainbow trout, Salmo gairdneri) extracellular toxins were purified by HPLC from the culture supernatants of Aeromonas hydrophila strain B32 which had been isolated from rainbow trout. A metalloprotease, MW 38 kDa, was stable at 56 degrees C for 10 min, had no cytotoxic activity and and LD50 of 150 ng/g fish. In narrow range isoelectric-focusing (IEF) the enzyme had 11 isomers with (pls) between 4.12 and 4.8. A serine protease (22 kDa) was stable at 56 degrees C for 10 min, possessed cytotoxic activity and had an LD50 of 150 ng/g fish. In IEF, multiple isomers possessed pls between 4.5-5.2. The haemolysin had alpha-haemolytic activity (68 kDa) multiple isomers in IEF with pl range 4.5-5.1 and an LD50 of 2 micrograms/g fish. It was stable after heating to 56 degrees C for 20 min, 60 degrees C for 10 min and possessed esterase activity on beta-naphthyl acetate. These latter properties suggest it may be a novel haemolysin distinct from alpha- and beta-haemolysin.
authors.affiliation: Department of Fundamental Biology, Faculty of Science, Orense, Spain.
authors.forename: L A
authors.initials: LA
authors.lastname: Rodriguez
authors.forename: A E
authors.initials: AE
authors.lastname: Ellis
authors.forename: T P
authors.initials: TP
authors.lastname: Nieto
mesh_terms: D000110:Acetylcholinesterase / Q000737:chemistry / Q000302:isolation & purification; D016980:Aeromonas hydrophila / Q000737:chemistry* / Q000472:pathogenicity; D000818:Animals; D005110:Extracellular Space / Q000201:enzymology*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000633:toxicity*; D008666:Metalloendopeptidases / Q000737:chemistry / Q000302:isolation & purification* / Q000633:toxicity*; D012697:Serine Endopeptidases / Q000737:chemistry / Q000302:isolation & purification* / Q000633:toxicity*; D014337:Trout / Q000382:microbiology*
chemical_list: D006460:Hemolysin Proteins; D000110:Acetylcholinesterase; D012697:Serine Endopeptidases; D008666:Metalloendopeptidases