Kinetics of Aspartic Acid Isomerization and Enantiomerization in Model Aspartyl Tripeptides under Forced Conditions
作者:Uwe Conrad、Alfred Fahr、Gerhard K.E. Scriba
DOI:10.1002/jps.22134
日期:2010.10
The aim of the present study was the determination of the isomerization and enantiomerization of aspartic acid (Asp) in tripeptides. Capillary electrophoresis (CE) assays were developed and validated allowing the simultaneous determination of the diastereomeric alpha-D/L-Asp and beta-D/L-Asp peptides. Rapid isomerization and enantiomerization were noted for peptides with the Phe-Asp-GlyOH sequence at
本研究的目的是确定三肽中天冬氨酸(Asp)的异构化和对映异构化。开发并验证了毛细管电泳(CE)分析方法,可同时测定非对映异构体α-D/ L-Asp和β-D/ L-Asp肽。注意到在pH 10和80℃下具有Phe-Asp-GlyOH序列的肽会快速异构化和对映异构,而由于苯基侧链的空间影响,Gly-Asp-PheOH被证明更稳定。假设琥珀酰亚胺中间体起关键作用的动力学模型用于拟合浓度对时间的数据。在L-Phe-α-L-Asp-GlyOH的孵育中,α-Asp/β-Asp肽的比例约为1:4,与文献数据一致。关于L-Asp和D-Asp肽,观察到的α-Asp/β-Asp比率分别约为1:3和1:5。在X-1位置的Phe立体化学影响L-Asp / D-Asp的比率,这暗示着相邻氨基酸的立体化学对Asp对映异构化的影响。观察到根据Asp肽的文献数据仅对整体Asp对映异构速率常数进行建模。如果使用天冬酰胺(A