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mutagenesis. [19] Since not much is known about how the C-C bond is formed or how in the absence of TE domain, O-C bond is formed, the Claisen condensation which controls the final cyclization cannot be monitored or modified for study.
It was shown that TE contains of the catalytic triad of Ser-His-Asp residues, which was confirmed by mutagenesis. [19-20] Reseachers showed that the CLC domain belongs to the α/β hydrolase family and consists of a deep, hydrophobic substrate binding chamber. They removed the phosphopantetheine arm of ACP to form a mutant ACP-TE domain to study hydrolysis by the TE domain as compared to that of the wild type. The mutant showed reduced hydrolytic activity proving that post- translational modification of ACP plays an important role in the hydrolytic activity of TE. Similarly, mutagenesis of each of the active site residues in the TE domain diminished its activity to a great extent. Finally, they carried out experiments to prove that the catalytic site residues were important in conducting the end Claisen cyclization. When the PksA activity was reconstituted with the mutants of the active residues, pyrone formation took place (O-C bond) while the wild type led to the formation of noranthrone (C-C bond). They also tested if pyrone could be converted to the norsolorinic acid by the TE domain but no
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 37 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 31 mutagenesis. [19] Since not much is known about how the C-C bond is formed or how in the absence of TE domain, O-C bond is formed, the Claisen condensation which controls the final cyclization cannot be monitored or modified for study. It was shown that TE contains of the catalytic triad of Ser-His-Asp residues, which was confirmed by mutagenesis. [19-20] Reseachers showed that the CLC domain belongs to the α/β hydrolase family and consists of a deep, hydrophobic substrate binding chamber. They removed the phosphopantetheine arm of ACP to form a mutant ACP-TE domain to study hydrolysis by the TE domain as compared to that of the wild type. The mutant showed reduced hydrolytic activity proving that post- translational modification of ACP plays an important role in the hydrolytic activity of TE. Similarly, mutagenesis of each of the active site residues in the TE domain diminished its activity to a great extent. Finally, they carried out experiments to prove that the catalytic site residues were important in conducting the end Claisen cyclization. When the PksA activity was reconstituted with the mutants of the active residues, pyrone formation took place (O-C bond) while the wild type led to the formation of noranthrone (C-C bond). They also tested if pyrone could be converted to the norsolorinic acid by the TE domain but no |
