title: Purification and characterisation of epithiospecifier protein from Brassica napus: enzymic intramolecular sulphur addition within alkenyl thiohydroximates derived from alkenyl glucosinolate hydrolysis.
abstract: Epithiospecifier protein (ESP), a ferrous ion dependent protein, has a potential role in regulating the release of elemental sulphur, nitriles, isothiocyanates and cyanoepithioalkanes from glucosinolates. Two classes of ESP polypeptides were purified with molecular masses of 39 and 35 kDa, and we show that the previously reported instability was conditionally dependent. The 39 kDa polypeptide was made up of two distinct isozymes (5.00, 5.14) whilst several were present for the 35 kDa form of ESP (5.40-5.66). An anti-ESP antibody reacted with both the 39 and 35 kDa ESP forms in Brassica napus and strongly with a polypeptide corresponding to the 35 kDa ESP form in Crambe abyssinica, but did not detect any ESP in Sinapis alba or Raphanus sativus. A cytochrome P-450 mediated iron dependent epoxidation type mechanism is suggested for ESP.
authors.affiliation: Department of Biological Sciences, Wye College, University of London, Wye, Ashford, UK.
authors.forename: H L
authors.initials: HL
authors.lastname: Foo
authors.forename: L M
authors.initials: LM
authors.lastname: Gronning
authors.forename: L
authors.initials: L
authors.lastname: Goodenough
authors.forename: A M
authors.initials: AM
authors.lastname: Bones
authors.forename: B
authors.initials: B
authors.lastname: Danielsen
authors.forename: D A
authors.initials: DA
authors.lastname: Whiting
authors.forename: J T
authors.initials: JT
authors.lastname: Rossiter
mesh_terms: D001937:Brassica / Q000378:metabolism*; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D005961:Glucosinolates / Q000378:metabolism*; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D010091:Oximes / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013455:Sulfur / Q000378:metabolism
chemical_list: D005961:Glucosinolates; D007527:Isoenzymes; D010091:Oximes; D010940:Plant Proteins; D013455:Sulfur