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Title: Inhibitor studies and PARA-aminobenzoic acid synthase
Author: Davies, G.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2003
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The research described in this thesis concerns a number of advances in the purification and assaying of the PABA synthase system organic synthesis of inhibitors of this enzyme system. The purification and characterisation of newly cloned six histidine tagged PABA synthase enzymes was carried out. The assay system used for amidotransferase-ADC synthase enzyme complex was refined and substrate kinetic data obtained. Results are compared to wild-type ADC synthase enzyme and data obtained for the assay system using ammonium in place of glutamine and amidotransferase. The synthesis of a number of aromatic compounds to act as mimics of 4-aimo-4-deoxychorismate has been accomplished. The formation of an enol pyruvyl side chain is achieved as a novel manner. Kinetic characterisation revealed a close structural analogue of 4-amino-4-deoxychroismate as the best inhibitor (Ki ca 20 mM) of PABA synthase so far. Synthesis was also carried out using aza-Cope and oxy-Cope rearrangements towards the formation of ADC and chorismate homologues with a methylene group present in place of the enol ether linkage. The biosynthesis of 2-fluorochorismate led to the discovery that this species was an irreversible inhibitor of the PABA synthase system. Work contained herein details the synthesis of a vinyl fluoride via a vinyl triflate and vinyl trialkylstannane utilising a lithium cuprate reagent. Fluorination is achieved using XeF2 in the presence of a catalytic amount of Ag(OTf). These mild conditions open up the possibility of the synthesis of more complex 2-fluorochorismate analogues. Dianion alkylation chemistry was used to add functionality to a molecule. Selenyl elimination/oxidation of a b-ketoester is used to form an extended delocalised system, which is thought to act as a precursor to a Michael acceptor for an enzyme nucleophile.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available