利用奈升流速液相層析奈電噴灑游離串聯式質譜法同時分析人類血紅蛋白上之甲基化及乙基化

Simultaneous Analysis of Human Hemoglobin Methylation and Ethylation by Nanoflow LC-Nanospray Ionization Tandem Mass Spectrometry

林芙蒂(Fu-Di Lin)

指導教授 ： 陳皓君

國立中正大學/理學院/化學暨生物化學系/碩士(2013年)

摘要

香菸中有許多致癌物，會引發肺癌、食道癌、膀胱癌等疾病，其中包含可與DNA進行烷基化反應的烷化試劑，除此之外蛋白質也會和這些反應試劑產生轉譯後修飾作用，像甲基化試劑會使DNA或蛋白質產生甲基化修飾，而乙基化試劑也會導致產生乙基化修飾。本研究希望能從蛋白質觀察吸菸對人的影響，以及探討吸菸者與非吸菸者在轉譯後修飾程度上是否有所差異。血紅蛋白具有取得容易、生命週期較長 (約120天) 、缺乏修復機制的優點，因此選擇人體中血紅蛋白來做為研究的對象。利用加入不同比例的甲基化試劑 (methyl methanesulfonate, MMS) 和乙基化試劑 (ethyl methanesulfonate, EMS) 在體外對市售人類血紅蛋白進行甲基化、乙基化修飾，而後經胰蛋白酶將修飾過後的血紅蛋白水解成胜肽，由線性離子阱串聯式質譜儀 (LTQ) 分析。目前已經確定會修飾上甲基化胺基酸的位置為α-globin上的1V、14W、23E、16K、20H、50H、72H、89H、90K，以及β-globin 上的1V、26E、77H、143H、144K，共14個修飾位置。用SRM 模式觀察不同濃度的MMS，對人類血紅蛋白上相對定量修飾的程度，其中有8個修飾位置具dose-dependent關係；會修飾上乙基化胺基酸的位置共14個，為α-globin上的1V、16K、50 H、56K、72H、90K、87H，以及β-globin上的1V、17K、66K、77H、92H、C93、95K，。用SRM 模式觀察EMS在不同反應時間下，對人類血紅蛋白上相對定量修飾的程度，並個別顯示具time-dependent關係。我們分析從各十個吸菸者與非吸菸者之血液中的血紅蛋白，目前發現吸菸者α- 50H、87H及β-17K的乙基化修飾程度高於非吸者，且具有統計學上的差異 (p＜0.05)，希望未來能作為一個吸菸的生物指標。

關鍵字

串聯式質譜儀 ； 乙基化 ； 甲基化 ； 血紅蛋白 ； 吸菸 ； 修飾程度

並列摘要

Many carcinogens are contained in cigarettes smoke, such as alkylating agents, which might be related to cancer formation. Human hemoglobin (Hb) is a target for biomarker research because of its easy accessibility, long life cycle, and the lack of the repair mechanisms. Hb reacts with alkylating agent and forms post-translational modifications such as methylation and ethylation. It might cause protein dysfunction and play an important role in cancer development. The goal of this study is to investigate the relationship between smoking and levels of Hb alkylation. Commercially available human Hb was modified by the methylating agent (methyl methanesulfonate, MMS) and ethyl reagent (ethyl methanesulfonate, EMS) separately. Modified Hb was digested by trypsin and analyzed by the nanoflow LC-nanospray ionization linear ion trap tandem mass spectrometry (nanoLC-NSI/MS/MS), followed by SEQUEST database search. The results show that methylation was found at 14 modified sites, including1V、14W、23E、16K、20H、50H、72H、89H、90K of α-globin and 1V、26E、77H、143H、144K of β-globin. Selected reaction monitoring (SRM) mode was used to analyze the degree of the relative quantification of modified human Hb by MMS, which shows 8 modified sites with a dose-dependent relationship. Ethylation was found at 14 modified sites including 1V、16K、50 H、56K、72H、87H、90K of α-globin and 1V、17K、66K、77H、92H、93C、95K of β-globin. The degree of the relative quantification of modified human Hb by EMS shows a time-dependent relationship. In this study, 10 smokers’ and 10 non-smokers’ samples were analyzed and statistically significance was calculated according to their levels of modification. Among all the modification sites, ethylation levels of α-50H, α-87H, and β-17K in Hb are higher in smokers than in non-smokers with p-values < 0.05. However, no statistically significance was found with methylation. This result should be helpful in measuring Hb ethylation level as a biomarker of smoking-related diseases.

並列關鍵字

MS/MS ； Ethylation ； Methylation ； Hemoglobin ； Smoke

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