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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/15176

Title: 利用醯基轉移酶(Dbv8)進行以輔酶A衍生物及醣胜肽抗生素結構骨架之生物組合化學研究
Expanding Glycopeptides Antibiotic Repertory: Utilizing a Novel Acyltransferase in Conjunction with Glycopeptide Pseudoaglycones and Coenzyme A Derivatives
Authors: Syue-Yi Lyu
Contributors: NTOU:Department of Food Science
Keywords: 醯基轉移酶;萬古黴素;最小抑菌濃度測試;醣胜肽抗生素
Date: 2008
Issue Date: 2011-06-30T08:07:33Z
Abstract: 抗甲氧基盤尼西林之金黃色葡萄球菌(methicillin-resistant Staphylcoccus aureus, MRSA)造成嚴重的院內感染問題,MRSA不僅對於大部份β-內醯胺(β-lactam)類抗生素具有抗藥性,已演變成具多重抗藥性菌株。Vancomycin為用於治療MRSA感染的最後一線醣胜肽抗生素,但隨著vancomycin使用增加,在選擇性的壓力下,對於vancomycin具抗藥性的菌株逐漸出現,此最後一線用藥將失去作用是可預見的,事實上這也是使用抗生素無法避免的困境,因此,我們必須不斷尋求新型抗生素,為避免無藥可用的一天到來。 A40926是由Actinomycete Nonomurea ATCC 39727所分離之天然醣胜肽抗生素,其生合成相關基因序列已被發現,其中參與A40926結構中長鏈醯基取代胺基葡萄醣酸之生合成途徑及關鍵酵素亦已被確認。Dbv8證實為一關鍵醯基轉移酶(acyltransferase),能催化轉移長鏈醯基從相對應的輔酶A衍生物(coenzyme A derivative)至A40926及teicoplanin葡萄糖胺擬醣苷 (teicoplanin pseudoaglycone)上。此醯化作用能增加藥物的疏水性,並延長其藥物半衰期,是藥物動力學上重要的影響因子。本論文是結合Dbv8與輔酶A衍生物對A40926之結構骨架進行修飾,期以創造出新抗生素庫,並以最小抑菌濃度測試(minimal inhibitory concentration test, MICs)篩選出更具效能之新型醣胜肽抗生素。 針對Dbv8之酵素基質專一性測試的結果,可歸納出輔酶A衍生物作為Dbv8基質之限制,輔酶A衍生物醯基中之α位置有甲基、苯環及羧基取代基,皆可能形成一立體障礙或靜電斥力,進而影響Dbv8之基團轉移活性。再者,我們發現teicoplanin family或vancomycin family之醣胜肽抗生素結構骨架皆可作為Dbv8的基質,產生屬於vancomycin類之新型醣胜肽抗生素。 另外,目前所分離純化之衍生物為teicoplanin pseudoaglycone, butyryl, hexanoyl, octanoyl, decanoyl, phenylacetyl取代基的teicoplanin pseudoaglycone,並由最小抑菌濃度測試決定出醯基長度之結構與抗菌活性之相關性,結果顯示,其醯基長度與抗菌活性成正比,即醯基長度越長之衍生抗生素,具有越佳的抗菌活性。 Oritavancin為一第三期臨床試驗之化學半合成醣胜肽抗生素,由chloroerymomycin所衍生而來,其抗菌活性較vancomycin高出1000倍之多,對於抗藥性菌株亦具有良好的效果,為一極具潛力的新型醣胜肽抗生素。我們利用Dbv8與3-naphylen propionyl輔酶A衍生物或4-biphenyl acetyl輔酶A衍生物,可將teicoplanin pseudoaglycone或vancomycin修飾成oritavancin結構類似物,咸信具有與oritavancin相同或更佳之生物活性,但是真實的活性仍待試驗來確認。
Vancomycin and teicoplanin are the two glycopeptide antibiotics currently used in clinics as last resort in treating serious infections caused by Gram-positive bacteria such as methicillin resistant Staphylococcus aureus (MRSA). Alarmingly, many cases of resistant S. aureus and enterococci to vancomycin have been reported in Japan, Europe, and the United States. The emergency of multidrug resistant Gram-positive bacteria have become an intractable public health issue. It is know that the eventual development of resistance owing to using antibiotics in clinic is inevitable. Therefore, there is a need to constantly develop more effective antibiotics to treat the life-threatening infections caused by the resistant strains. Biological engineering of existing drugs has turn out to be an effective and specific approach for development of new antibiotics. A40926 is a natural glycopeptide antibiotic, which was isolated from Actinomycete Nonomurea ATCC 39727. The pathway towards N-acyl aminoglucuronic acid moiety in A40926 has been reported recently. Dbv8 was characterized as the key acyltransferase by which an acyl moiety from acyl-CoA donors is transfered to the aminosugar of teicoplanin pseudoaglycone. The natural found A40926 is a mixture of compound with various acyl side chain. The substrate tolerance of Dbv8 led us to consider to further explore the substrate dimension of Dbv8. As a result, we used Dbv8 as a chemoenzymatic tool to generate a library of novel glycopeptide antibiotics. In the current setting, more than 30 novel glycopeptide antibiotics on the basis of vancomycin or teicoplanin have been made. The SAR (relationship of structure and antibacterial activity) of various length of acyl side chain of the N-acyl aminoglucose moiety in teicoplanin against Staphylococcus aureus ATCC 29213 (an antibitics sensitive strain) and MU-50 (a vancomycin resistant S. aureus) has been determined. The result is that the carbon length of acyl side chain is found critical and the bactericidal activity is proportion to the carbon length. Oritavancin that is a chemical derivative of chloroerymomycin is currently under phase III clinical trial. It has been shown promising with 1000 fold antibiotic activity high than vancomycin. By testing substrate tolerance of Dbv8 , we have created 3-naphylen propionyl and 4-biphenyl acetyl teicoplanin / vancomycin derivatives. We believe these derivatives would possess equal or even better activity than oritavancin. However, the authentic activities of these compounds are required to be determined in the future.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M95320039
Appears in Collections:[食品科學系] 博碩士論文

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