CE-MS Identification of Amino Acid Sequence Inversion as a New Degradation Pathway of an Aspartyl Model Tripeptide
CE-MS Identification of Amino Acid Sequence Inversion as a New Degradation Pathway of an Aspartyl Model Tripeptide
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DOI：
10.1007/s10337-012-2306-5
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发表时间：
2012-10-01
期刊：
影响因子：
1.7
通讯作者：
Scriba, Gerhard K. E.
中科院分区：
文献类型：
--
作者：
Brueckner, Christin;Bunz, Svenja-Catharina;Scriba, Gerhard K. E.
采用CE-MS鉴定在80 A ℃下在pH 7.4的水溶液中加热的模型三肽Phe-alpha-Asp-Gly的两种未知降解产物。两种化合物显示出基本相同的质谱，表明存在肽非对映异构体。m/z 338处的[M + H]（+）-离子表明由氨基酸Phe、Gly和Asp组成的三肽。片段化模式表明Phe不位于N-末端。随后，合成线性肽α-Asp-Phe-Gly和支链肽Asp（Gly）-Phe，并通过CE-MS进行分析。合成的α-Asp-Phe-Gly的质谱与未知化合物的质谱相同，证实了降解产物的结构。Asp（Gly）-Phe呈现复杂的裂解模式。总之，氨基酸序列倒位代表了Phe-alpha-Asp-Gly在pH 7.4下除了已知的异构化、对映异构化、环化为二酮哌嗪衍生物和主链水解的另一种降解途径。氨基酸序列的重排的机制提出通过氮杂桥连的中间体进行。
CE-MS was employed to identify two unknown degradation products of the model tripeptide Phe-alpha-Asp-Gly heated at 80 A degrees C in aqueous solution at pH 7.4. Both compounds displayed essentially identical mass spectra indicating the presence of peptide diastereomers. The [M + H](+)-ion at m/z 338 suggested a tripeptide composed of the amino acids Phe, Gly and Asp. The fragmentation pattern indicated that Phe was not located at the N-terminus. Subsequently, the linear peptide alpha-Asp-Phe-Gly and the branched peptide Asp(Gly)-Phe were synthesized and analyzed by CE-MS. The mass spectrum of synthetic alpha-Asp-Phe-Gly was identical to that of the unknown compounds confirming the structure of the degradation products. Asp(Gly)-Phe displayed a complex fragmentation pattern. In conclusion, amino acid sequence inversion represents another degradation pathway of Phe-alpha-Asp-Gly at pH 7.4 besides known reactions including isomerization, enantiomerization, cyclization to diketopiperazine derivatives and backbone hydrolysis. The mechanism of the rearrangement of the amino acid sequence is proposed to proceed via an aza-bridged intermediate.