School of Biological Sciences, The University of Hong Kong , Pokfulam Road, Hong Kong, PR China.
Chem Res Toxicol. 2011 Aug 15;24(8):1304-11. doi: 10.1021/tx2001916. Epub 2011 Jul 1.
In the present study, the dual effects of phloretin and phloridzin on methylglyoxal (MGO)-induced glycation were investigated in three N(α)-acetyl amino acid (arginine, cysteine, and lysine) models and three N-terminal polypeptide (PP01, PP02, and PP03 containing arginine, cysteine, and lysine, respectively) models. In both N(α)-acetyl amino acids and N-terminal polypeptides models, the arginine residue was confirmed as the major target for modification induced by MGO. Meanwhile, MGO modification was significantly inhibited by the addition of phloretin or phloridzin via their MGO-trapping abilities, with phloretin being more effective. Interestingly, the cysteine residue was intact when solely incubated with MGO, whereas the consumption of N(α)-acetylcysteine and PP02 was promoted by the addition of phloretin. Additional adducts, [N(α)-acetylcysteine + 2MGO + phloretin-H(2)O] and [2N(α)-acetylcysteine + 2MGO + phloretin-2H(2)O] were formed in the model composed of N(α)-acetylcysteine, MGO, and phloretin. Another adduct, [PP02 + 2MGO + phloretin-H(2)O] was observed in the model composed of PP02, MGO, and phloretin. The generation of adducts indicates that phloretin could directly participate in the modification of the cysteine residue in the presence of MGO. When creatine kinase (model protein) was exposed to MGO, the addition of phloridzin did not show a significant effect on retaining the activity of creatine kinase impaired by MGO, whereas the addition of phloretin completely inactivated creatine kinase. Results of the mass spectrometric analysis of intact creatine kinase in different models demonstrated that phloretin could directly participate in the reaction between creatine kinase and MGO, which would lead to the inactivation of creatine kinase. Furthermore, the addition of N(α)-acetylcysteine was found to maintain the activity of creatine kinase incubated with phloretin and MGO. These results showed that phloretin and phloridzin could inhibit the modification of the arginine residue by MGO and that phloretin could directly participate in the reaction between the thiol group and MGO.
在本研究中，研究了根皮苷和根皮素对甲基乙二醛（MGO）诱导的糖化的双重作用，分别在三个 N(α)-乙酰氨基酸（精氨酸、半胱氨酸和赖氨酸）模型和三个 N 末端多肽（分别含有精氨酸、半胱氨酸和赖氨酸的 PP01、PP02 和 PP03）模型中进行了研究。在 N(α)-乙酰氨基酸和 N 末端多肽模型中，确定精氨酸残基是 MGO 诱导修饰的主要靶标。同时，通过其 MGO 捕获能力，根皮苷或根皮素的添加显著抑制了 MGO 修饰，其中根皮苷的效果更显著。有趣的是，当仅与 MGO 孵育时，半胱氨酸残基保持完整，而添加根皮苷则促进 N(α)-乙酰半胱氨酸和 PP02 的消耗。在由 N(α)-乙酰半胱氨酸、MGO 和根皮苷组成的模型中形成了加合物 [N(α)-乙酰半胱氨酸+2MGO+根皮苷-H(2)O] 和 [2N(α)-乙酰半胱氨酸+2MGO+根皮苷-2H(2)O]。在由 PP02、MGO 和根皮苷组成的模型中观察到另一种加合物 [PP02+2MGO+根皮苷-H(2)O]。加合物的形成表明，在存在 MGO 的情况下，根皮苷可以直接参与半胱氨酸残基的修饰。当肌酸激酶（模型蛋白）暴露于 MGO 时，添加根皮素对保留受 MGO 损害的肌酸激酶活性没有显著影响，而添加根皮苷则完全使肌酸激酶失活。不同模型中完整肌酸激酶的质谱分析结果表明，根皮苷可以直接参与肌酸激酶与 MGO 之间的反应，从而导致肌酸激酶失活。此外，添加 N(α)-乙酰半胱氨酸被发现可以维持与根皮苷和 MGO 孵育的肌酸激酶的活性。这些结果表明，根皮苷和根皮素可以抑制 MGO 对半胱氨酸残基的修饰，并且根皮苷可以直接参与巯基和 MGO 之间的反应。
