Yoshitake Jun, Shibata Takahiro, Chikazawa Miho, Uchida Koji
Institute of Nano-Life-Systems, Institutes of Innovation for Future Society, Nagoya University, Nagoya, Japan.
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
Free Radic Res. 2022 Nov-Dec;56(11-12):749-759. doi: 10.1080/10715762.2023.2174865. Epub 2023 Feb 7.
Protein -pyrrolation, which converts lysine residues to -pyrrole-l-lysine (pyrK), is a naturally occurring covalent modification. The pyrrolated proteins have a unique property of binding to DNA-staining agents, such as SYBR Green I (SG), and anti-DNA antibodies, suggesting a physiologically relevant modification that gives rise to DNA mimic protein. These properties of pyrrolated protein are suggested to be associated with innate and autoimmune responses. Short-chain aldehydes derived from lipid peroxidation are thought to be involved in the formation of pyrK. We now report that similar lysine -pyrrolation also occurs during the metal-catalyzed oxidation of proteins with ascorbate. When human serum albumin (HSA) was incubated with Fe/ascorbate in the presence and absence of docosahexaenoic acid, the protein was converted to SG-binding proteins even without the polyunsaturated fatty acid. The formation of SG-binding proteins by Fe/ascorbate was accompanied by the formation of pyrK, which was also detected in ascorbate-treated hemoglobin. Moreover, the metal-catalyzed oxidation of ascorbate produced the pyrrolation factors, glycolaldehyde and glyoxal. These results and the observations that sera from autoimmune-prone MRL- mice recognized modified proteins with Fe/ascorbate and with glycolaldehyde/glyoxal suggest that the autoxidation of ascorbate, as well as lipid peroxidation, can be a source of autoantigenic -pyrrolated proteins. Our findings revealed a possible function of ascorbate as an endogenous source of pyrrolated proteins and suggested that the pyrK residues generated in proteins may play a role in the innate and autoimmune responses associated with the oxidative metabolism of ascorbate.
蛋白质-吡咯化作用可将赖氨酸残基转化为-吡咯-1-赖氨酸（pyrK），这是一种天然存在的共价修饰。吡咯化的蛋白质具有与DNA染色剂（如SYBR Green I，SG）和抗DNA抗体结合的独特性质，提示这是一种具有生理相关性的修饰，可产生模拟DNA的蛋白质。吡咯化蛋白质的这些性质被认为与先天性和自身免疫反应有关。脂质过氧化产生的短链醛类被认为参与了pyrK的形成。我们现在报告，在蛋白质与抗坏血酸的金属催化氧化过程中也会发生类似的赖氨酸-吡咯化作用。当人血清白蛋白（HSA）在有和没有二十二碳六烯酸的情况下与铁/抗坏血酸一起孵育时，即使没有多不饱和脂肪酸，该蛋白质也会转化为与SG结合的蛋白质。铁/抗坏血酸导致与SG结合的蛋白质形成的同时伴有pyrK的形成，在抗坏血酸处理过的血红蛋白中也检测到了pyrK。此外，抗坏血酸的金属催化氧化产生了吡咯化因子，乙醇醛和乙二醛。这些结果以及自身免疫易感的MRL-小鼠血清能识别经铁/抗坏血酸以及乙醇醛/乙二醛修饰过的蛋白质这一观察结果表明，抗坏血酸的自氧化以及脂质过氧化都可能是自身抗原性吡咯化蛋白质的来源。我们的研究结果揭示了抗坏血酸作为吡咯化蛋白质内源性来源的一种可能功能，并提示蛋白质中产生的pyrK残基可能在与抗坏血酸氧化代谢相关的先天性和自身免疫反应中发挥作用。
