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Title: Synthetic investigations of PKS starter unit specificity
Author: Frost, E. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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The incorporation of aromatic starter units into polyketide molecules will provide an interesting array of compounds. This work addresses a variety of synthetic methods for the investigation of such incorporation and includes the synthesis of substrates for in vitro enzyme assays and standards for the analysis of the results. An investigation of the incorporation of benzyoyl-CoA and a series of aromatic diketides by DEBS1-TE revealed broader specificity of this enzyme than had previously been reported. All diketide intermediates tested (see diagram, R = Ph, CH2Ph, CH2CH2Ph) assayed in vitro using DEBS1-TE were shown to be incorporated into the corresponding δ-lactone products. Benzoyl-CoA was also shown to be a substrate for DEBS1-TE. These results were verified by the use of standards synthesised during the course of this study. (Fig. 8781A) The synthesis of δ-aromatically substituted triketide lactone standards with and without substitution at the γ-position is reported in this work. These compounds have been used to determine the role of domains within the soraphen A PKS loading module. The AT1a domain of the soraphen A PKS loading module has been shown to confer specificity for a benzoate starter onto a hybrid DEBS1-TE construct in vivo. The synthesis of β-keto NAC thioesters (see diagram R = CH2Ph, CH2CH2Ph) and α,γ-unsubstituted δ-lactones (see diagram, R = CH2Ph, CH2CH2Ph) has been achieved. These compounds will be used as substrates and standards for future experiments in PKS specificity. (Fig. 8781B) The incorporation of double bond moieties into the starter unit position of polyketide molecules has been addressed. This is with an aim to produce natural products which will be amenable to chemical modification by semi-synthetic approaches. The synthesis of enzyme substrates and synthetic standards for this study has been achieved (see diagram). Compounds are ready for in vitro studies with DEBS1-TE. (Fig. 8781C) This study has demonstrated the incorporation of aromatic starter units by PKS enzymes, both in vivo and in vitro.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available