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LovB lacks a thioesterase (TE) domain which would catalyze the release of the end product. The failure of LovB to release 1 is surprising because the heterologous host Aspergillus nidulans expressing LovB and LovC produces substantial quantities of dihydromonacolin L. [25] Studies were then conducted to study the cleavage of the LovB ACP-thioester of 1 by TEs involved in fatty acid biosynthesis or unrelated PKS pathways. To test this, a broad spectrum fungal TE domain from a Gibberella zeae PKS13 [26], was added to the in vitro reaction. [11]
Fascinating results were obtained that confirmed certain expectations. Release of product dihydromonacolin L acid was seen with high enzyme turnover which demonstrated that PKS13 supports the generation of dihydromonacolin L acid linearly for about 12 hours to give a >10-fold increase in product. The catalytic triad of the PKS13 TE played a major role in the enzyme turnover, and mutation in the active site histidine to alanine completely abolished the activity. Other fungal TE domains, such as the Gibberella fujikuroi PKS4 TE domain [12], also facilitate the release of dihydromonacolin L acid, although to half the amount seen with PKS13. In contrast, TE domains from bacterial type I PKSs, such as that from the erythromycin PKS [27], fail to cause release of product dihydromonacolin L acid. These experiments suggest that cleavage of
Object Description
| Title | Fungal polyketides -- Review of recent findings |
| Author | Jain, Sofina M. |
| Author email | sofinaja@usc.edu; sofinajain27@gmail.com |
| Degree | Master of Science |
| Document type | Thesis |
| Degree program | Pharmacy / Pharmaceutical Sciences |
| School | School of Pharmacy |
| Date defended/completed | 2011-05-04 |
| Date submitted | 2011 |
| Restricted until | Unrestricted |
| Date published | 2011-05-05 |
| Advisor (committee chair) | Wang, Clay C. C. |
| Advisor (committee member) |
Okamoto, Curtis Toshio Shen, Wei-Chiang |
| Abstract | Fungal polyketides are a group of bioactive compounds which have found use in humans as anti-cholesterol, anti-cancer and antibiotic agents. These are synthesized by a group of enzymes called the polyketide synthases (PKSs) which are found in fungi as well as bacteria. PKSs are classified as type I, II and III. All fungal PKSs are type I iterative polyketide synthases which means they use a set of catalytic functions by a group of active domains in repetitive cycles to give the end product. Type I enzymes contain multidomains that catalyze a set of reactions.; The minimal PKS contains the domains ketosynthase (KS), acyltransferase (AT) and acyl carrier protein (ACP). The three types of PKSs are non-reduced polyketide synthases (NR-PKSs), highly-reduced polyketide synthases (HR-PKSs) and partially-reduced polyketide synthases (PR-PKSs). This classification is another form separate from type I, II and III. This paper discusses the recent research into further details of the SAT, PT and TE domain of the NR-PKSs and also recent advances in the HR-PKSs. This paper will also discuss the role of NADPH, SAM and CON domain in the HR-PKSs. We will also discuss the two off-loading mechanism of HR-PKSs that were seen in recent papers. While little research is done on PR-PKSs, NR-PKS and HR-PKS are extensively being worked on.Recent findings have brought us a step closer to the domains of the PKSs and promise us a better clearer understanding of this complex multidomain entity. |
| Keyword | fungal polyketides; HR-PKS; NR-PKS; PT domain; SAT domain; TE domain |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m3914 |
| Contributing entity | University of Southern California |
| Rights | Jain, Sofina M. |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-jain-4552 |
| Archival file | uscthesesreloadpub_Volume40/etd-jain-4552.pdf |
Description
| Title | Page 50 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 44 LovB lacks a thioesterase (TE) domain which would catalyze the release of the end product. The failure of LovB to release 1 is surprising because the heterologous host Aspergillus nidulans expressing LovB and LovC produces substantial quantities of dihydromonacolin L. [25] Studies were then conducted to study the cleavage of the LovB ACP-thioester of 1 by TEs involved in fatty acid biosynthesis or unrelated PKS pathways. To test this, a broad spectrum fungal TE domain from a Gibberella zeae PKS13 [26], was added to the in vitro reaction. [11] Fascinating results were obtained that confirmed certain expectations. Release of product dihydromonacolin L acid was seen with high enzyme turnover which demonstrated that PKS13 supports the generation of dihydromonacolin L acid linearly for about 12 hours to give a >10-fold increase in product. The catalytic triad of the PKS13 TE played a major role in the enzyme turnover, and mutation in the active site histidine to alanine completely abolished the activity. Other fungal TE domains, such as the Gibberella fujikuroi PKS4 TE domain [12], also facilitate the release of dihydromonacolin L acid, although to half the amount seen with PKS13. In contrast, TE domains from bacterial type I PKSs, such as that from the erythromycin PKS [27], fail to cause release of product dihydromonacolin L acid. These experiments suggest that cleavage of |
