title: Determination and isolation of a thioesterase from passion fruit (Passiflora edulis Sims) that hydrolyzes volatile thioesters.
abstract: Volatile organosulfur compounds (VOSCs) are high impact aroma chemicals characteristic of tropical fruits which are active as both free thiols and the respective thioesters. Using a simple and sensitive colorimetric enzyme assay, a thioesterase activity toward VOSCs has been identified in ripening purple passion fruit ( Passiflora edulis Sims). The assay was based on determining the release of free thiols from 2-methyl-3-furanthiol acetate using Ellman's reagent. The major thioesterase in the fruit was found to be a wall-bound protein in the mesocarp. The extracted enzyme activity was purified 150-fold and shown to be associated with a 43 kDa monomeric serine hydrolase which was selectively labeled with a fluorophosphonate suicide probe. MS-MS sequencing identified the thioesterase as a class 13 glycoside hydrolase, most similar to pectin acetylesterase, an enzyme involved in cell wall modifications in the peel of a number of fruit. Our results suggest that cell wall hydrolases in tropical fruit may have additional useful roles in biotransforming VOSCs.
authors.affiliation: Robert.Edwards@durham.ac.uk.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Tapp
authors.forename: Ian
authors.initials: I
authors.lastname: Cummins
authors.forename: David
authors.initials: D
authors.lastname: Brassington
authors.forename: Robert
authors.initials: R
authors.lastname: Edwards
mesh_terms: D004950:Esterases / Q000302:isolation & purification* / Q000378:metabolism*; D005638:Fruit / Q000201:enzymology; D005663:Furans / Q000378:metabolism; D006868:Hydrolysis; D009812:Odorants / Q000032:analysis; D029598:Passiflora / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014835:Volatilization
chemical_list: D005663:Furans; D013438:Sulfhydryl Compounds; D004950:Esterases; C443400:2-methyl-3-furanthiol