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The aim of this research was to determine the relative importance of glutathione S-transferase (GST) mediated herbicide and fungicide detoxification in wheat plants and to functionally characterise GSTs cloned from phytopathogenic fungi. Wheat seedlings treated with and without safeners were used for in vivo and in vitro pesticide metabolism studies with the herbicide fenoxaprop-P-ethyl and the fungicide fluquinconazole, which are both known to undergo glutathione conjugation. Fenoxaprop-P-ethyl underwent rapid detoxification by this route and the rates of metabolism were enhanced in safener treated wheat. In contrast, fluquinconazole was poorly metabolised with only a small proportion detoxified by glutathlonylation irrespective of whether or not the plants were safener treated. Subsequent studies confirmed that whereas fenoxaprop was a substrate for wheat GSTs, fluquinconazole was not. Similarly, when a diverse range of systemic and contact fungicides was tested, none were found to undergo conjugation mediated by wheat GSTs, even though several compounds underwent conjugation with glutathione in alkaline conditions. Metabolite profiling by HPLC-MS established that the alternative thiol present in wheat, hydroxymethyl glutathione, was used in addition to glutathione in fenoxaprop detoxification. The S-conjugates were then further metabolised by peptidases and glucosyl- and malonyl transferases to yield polar derivatives such as the cysteinyl-malonyl-glucosyl derivative. This rapid processing was in contrast to that determined in herbicide-susceptible and herbicide-resistant black-grass, where the glutathione derivative was the major metabolite of fenoxaprop. Using an informatics approach, GSTs in IVIagnaporthe griseae and Phytoptithora infestans were identified cloned and then expressed in E. coli, with the pure enzymes assayed for glutathione-dependent activities. MgGSTX1 of Magnaporthe griseae was found to be a member of a novel class of GSTs (termed xi class) and was shown to function as a thioltransferase, with a specific activity of 50.4 ± 3.4 nKat mg (^-1)protein. Unusually, the catalytic mechanism of thiol transfer was insensitive to the alkylating agent iodoacetamide, indicating that free cysteines were not involved in catalysis. MgGSTX1 did not conjugate any of the experimental xenobiotics tested with GSH. The theta class GST P/GSTT1 cloned from P. infestans exhibited glutathione peroxidase activity and readily detoxified fungitoxic oxylipins produced by potato as antimicrobial defence by potato through the action of lipoxygenases. Using anti-sera raised against the purified recombinant protein, immunoblotting experiments revealed expression of P/GSTT1 in the in vitro cultured fungus as well as during colonisation of potato. P/GSTT1 did not demonstrate GSH conjugating toward any of the xenobiotic substrates tested including herbicides and fungicides. Based on the sequences of GSTs identified in this study an extension of the existing classification system is suggested to include the GSTs of fungal phytopathogens

The properties of the perfluoropolymer sulphonic acid resin, sold under the trade name of Nafion have been examined. The use of Nafion as a support for transition metal catalysts has been studied in the context of alternative support systems. It has been demonstrated that transition metal complexes are readily incorporated into Nafion, provided they are either ionic in nature or contain ligands which are organic acid anions or ligands which can be protonated. Nafion used as a support has been successfully recycled and forms of Nafion with modified functional groups have been successfully synthesised. In order to explore the scope of Nafion as a catalyst support, a range of reactions has been investigated, the main purpose being comparison between the performance of a catalyst used homogeneously to its performance supported in Nafion. The hydroesterification of ethene to methyl propanoate was studied using several palladium complexes as catalysts. The ejects of temperature, CO pressure, catalyst loading and ligand to metal ratio on yields of product were recorded, using the most effective of the supported palladium catalyst systems. Yields of methyl propanoate using Nafion supported complex as catalyst were higher than the same catalyst used unsupported under comparable conditions. The hydrogenation of cyclohexene, dimethyl maleate and nitrotoluene was accomplished using the complexes [Ir(COD)(PPh(_2)Me)]PF(_6), [Rh(NBD){Fe(C(_5)H(_4)PPr(_2))(_2)}]BF(_4) and [RhCl(Ph(_2)P-NC(_5)H(_10))(_3)]. Yields of hydrogenation products using Nafion supported complexes were comparable or higher than yields obtained homogeneously. The hydrofonnylati n of hexene was carried out using a series of complexes of the form [Rh(NBD)L(_2)]BF(_4) where L represents a phosphine. Yields of aldehydes and normal to branched ratios were slightly lower using Nafion supported complexes in comparison to the homogeneous case. The production of substituted pyridines from propyne and acetonitrile was attempted using cobalt complexes coordinated to modified cyclopentadiene rings without success.