title: Isolation and purification of an enzyme hydrolyzing ochratoxin A from Aspergillus niger.
abstract: Ochratoxin A is a mycotoxin produced by several Aspergillus and some Penicillium species which may be present in food and feed products. It can be enzymatically hydrolyzed into ochratoxin alpha and L: -beta-phenylalanine, thereby decreasing its toxicity. The ochratoxin A degradation capacity of Aspergillus niger is well known and here we report the isolation and purification of a novel enzyme from A. niger that hydrolyzes this mycotoxin. A wheat germ medium supplemented with ochratoxin A was used to produce the enzyme, which was purified from culture filtrate by acetone precipitation and anion exchange chromatography. An overall purification of 2.5-fold with a recovery of 68% and a final specific activity of 36 U/mg was obtained. The enzyme is a metalloenzyme as it was inhibited at 10 mM EDTA, whereas PMSF had no effect. The ochratoxin A hydrolytic enzyme presented a V (max) of 0.44 microM/min and a K (m) of 0.5 mM when the reaction was carried out at pH 7.5 and 37 degrees C.
authors.affiliation: IBB- Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, Universidade do Minho, Campus de Gualtar, Brague, 4710-057, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Abrunhosa
authors.forename: Armando
authors.initials: A
authors.lastname: Venâncio
mesh_terms: D001234:Aspergillus niger / Q000187:drug effects / Q000201:enzymology*; D043422:Carboxypeptidases A / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005656:Fungal Proteins / Q000037:antagonists & inhibitors* / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D009793:Ochratoxins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D009793:Ochratoxins; C025589:ochratoxin A; D043422:Carboxypeptidases A