Oxidative stress, an excess of reactive oxygen species (ROS), may lead to oxidative post-translational modifications of proteins resulting in the cleavage of the peptide backbone, known as α-amidation, and formation of fragments such as peptide amides and α-ketoacyl peptides (α-KaP). In this study, we first compared different approaches for the synthesis of different model α-KaP and then investigated their stability compared to the corresponding unmodified peptides. The stability of peptides was studied at room temperature or at temperatures relevant for food processing (100 °C for cooking and 150 °C as a simulation of roasting) in water, in 1% (m/v) acetic acid or as the dry substance (to simulate the thermal treatment of dehydration processes) by HPLC analysis. Oxidation of peptides by 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ) proved to be the most suited method for synthesis of α-KaPs. The acyl side chain of the carbonyl-terminal α-keto acid has a crucial impact on the stability of α-KaPs. This carbonyl group has a catalytic effect on the hydrolysis of the neighboring peptide bond, leading to the release of α-keto acids. Unmodified peptides were significantly more stable than the corresponding α-KaPs. The possibility of further degradation reactions was shown by the formation of Schiff bases from glyoxylic or pyruvic acids with glycine and proven through detection of transamination products and Strecker aldehydes of α-keto acids by HPLC–MS/MS. We propose here a mechanism for the decomposition of α-ketoacyl peptides.

氧化应激（过量的活性氧（ROS））可能导致蛋白质的氧化翻译后修饰，从而导致肽主链裂解（称为α-酰胺化），并形成片段（如肽酰胺和α-酮酰基）肽（α- KaP）。在这项研究中，我们首先比较了合成不同模型α- KaP的不同方法，然后研究了与相应未修饰肽相比的稳定性。在室温或与食品加工相关的温度（烹饪时为100°C，模拟为焙烧为150°C）中，以1％（m / v乙酸或干物质（模拟脱水过程的热处理），通过HPLC分析。2,5-二叔丁基-1,4-苯醌（DTBBQ）氧化肽被证明是最适合合成α- KaPs的方法。羰基-终端α酮酸的酰基侧链上具有的稳定性产生重要影响α -KaPs。该羰基对相邻肽键的水解具有催化作用，导致α-酮酸的释放。未修饰的肽比相应的α稳定得多-KaPs。由乙醛酸或丙酮酸与甘氨酸形成席夫碱表明了进一步降解反应的可能性，并通过HPLC-MS / MS检测α-酮酸的氨基转移产物和Strecker醛得到了证实。我们在这里提出α-酮酰基肽分解的机制。