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49
only the vector while the second type contained FUM8. When pYES2/FUM8 yeast cells were incubated with C18-S-ACP as compared to that with only vector, 2 new peaks were seen. These two peaks were not seen if C-18-CoA, ACP, PLP or L-alanine were omitted. GC-MS analysis of the peaks proved that FUM8 is capable of catalyzing the PLP dependent release of the C1 chain from the ACP in addition to the incorporation of two further carbons and an amino group. The stereospecificity of the ketoreductase enzyme is observed since the 3-keto group of 2 and 3 are not reduced further by the sphinganine-3-ketoreductase in the yeast, attributed to the fact that sphingolipids have 3R hydroxyl while fumonisin has 3S hydroxyl. Acyl chains of length C12-C20 can be incorporated in the polyketide but it has been previously seen that it selectively incorporated a C18 carbon chain. Further, KS-domain replacement experiments as well as PKS functional complementation experiments have proved further that the chain releasing enzyme and its substrate specificity play a key role in the synthesis of the distinct polyketides in this fungus. To summarize, it has been shown that some HR-PKSs use PLP as a cofactor to release product from the ACP. In doing so, it uses a carbon nucleophile to attack the terminal carbonyl of the acyl-S-PKS to release the polyketide. A very important point to consider
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 55 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 49 only the vector while the second type contained FUM8. When pYES2/FUM8 yeast cells were incubated with C18-S-ACP as compared to that with only vector, 2 new peaks were seen. These two peaks were not seen if C-18-CoA, ACP, PLP or L-alanine were omitted. GC-MS analysis of the peaks proved that FUM8 is capable of catalyzing the PLP dependent release of the C1 chain from the ACP in addition to the incorporation of two further carbons and an amino group. The stereospecificity of the ketoreductase enzyme is observed since the 3-keto group of 2 and 3 are not reduced further by the sphinganine-3-ketoreductase in the yeast, attributed to the fact that sphingolipids have 3R hydroxyl while fumonisin has 3S hydroxyl. Acyl chains of length C12-C20 can be incorporated in the polyketide but it has been previously seen that it selectively incorporated a C18 carbon chain. Further, KS-domain replacement experiments as well as PKS functional complementation experiments have proved further that the chain releasing enzyme and its substrate specificity play a key role in the synthesis of the distinct polyketides in this fungus. To summarize, it has been shown that some HR-PKSs use PLP as a cofactor to release product from the ACP. In doing so, it uses a carbon nucleophile to attack the terminal carbonyl of the acyl-S-PKS to release the polyketide. A very important point to consider |
