title: Characterization of epoxide hydrolase activity in Alternaria alternata f. sp. lycopersici. Possible involvement in toxin production.
abstract: Using trans-diphenylpropane oxide (tDPPO) as a substrate, we measured epoxide hydrolase (EH) activity in subcellular fractions of Alternaria alternata f. sp. lycopersici (Aal), a fungus that produces host-specific toxins. The activity was mainly (> 99.5%) located in the soluble fraction (100,000 x g supernatant) with the optimum pH at 7.4. An increase of toxin production between days 3 and 9 found in a Aal liquid culture over a 15 days period was concomitant with a period of high EH activity. EH activity remained constant during the same period in an Alternaria alternata culture, a fungus which does not produce toxin. In vivo treatment of Aal culture with the peroxisome proliferator clofibrate stimulated EH activity by 83% and enhanced toxin production 6.3 fold. Both 4-fluorochalcone oxide (4-FCO) and (2S,3S)-(-)-3-(4-nitrophenyl)-glycidol (SS-NPG) inhibited EH activity in vitro with a I50 of 23 +/- 1 microM and 72 +/- 19 microM, respectively. The possible physiological substrate 9,10-epoxystearic acid was hydrolyzed more efficiently by Aal sEH than the model substrates trans- and cis-stilbene oxide (TSO and CSO) and trans- and cis-diphenylpropane oxide (tDPPO and cDPPO).
authors.affiliation: Laboratoire d'Enzymologie Cellulaire et Moléculaire, Institut de Biologie Moléculaire des Plantes, Strasbourg, France.
authors.forename: F
authors.initials: F
authors.lastname: Pinot
authors.forename: E D
authors.initials: ED
authors.lastname: Caldas
authors.forename: C
authors.initials: C
authors.lastname: Schmidt
authors.forename: D G
authors.initials: DG
authors.lastname: Gilchrist
authors.forename: A D
authors.initials: AD
authors.lastname: Jones
authors.forename: C K
authors.initials: CK
authors.lastname: Winter
authors.forename: B D
authors.initials: BD
authors.lastname: Hammock
mesh_terms: D000528:Alternaria / Q000201:enzymology* / Q000254:growth & development; D002994:Clofibrate / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D004851:Epoxide Hydrolases / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000382:microbiology; D009183:Mycotoxins / Q000378:metabolism; D013997:Time Factors
chemical_list: D005656:Fungal Proteins; D009183:Mycotoxins; D004851:Epoxide Hydrolases; D002994:Clofibrate