Ooizumi Tooru, Xiong Youling L
Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuen-Cho, Obama 917-0003, Japan.
J Agric Food Chem. 2004 Jun 30;52(13):4303-7. doi: 10.1021/jf035521v.
Biochemical changes of myosin in chicken myofibrils exposed to nonenzymatic, hydroxyl radical generation systems (HRGS) were investigated by means of cross-linking reaction, ATPase activity, salt solubility, and 40% saturated ammonium sulfate (AS) extractability. HRGS treatment of myofibrils caused cross-linking of myosin heavy chains (MHC) via disulfide bonding, an increase in Ca-ATPase activity, and a decrease in K-ATPase activity, suggesting that thiol groups of myosin including those at the active site were modified. The specific changes depended on the concentrations of H(2)O(2) in HRGS as well as the weight ratio of H(2)O(2) to myofibrils. On the other hand, the decrease in salt solubility or AS extractability of myosin in HRGS-treated samples proceeded slowly when compared with the cross-linking reaction of MHC, indicating that considerable amounts of myosin biopolymers remained hydrophilic in the ionic solutions. The results demonstrated that initial cross-linking of MHC occurred inside the myosin molecule, and this was followed by progressive aggregation of myosin molecules through intermolecular cross-linking. Oxidation under the current experimental condition decreased the gel-forming ability of myofibrillar proteins, which coincided with the progress of the intra- and intermolecular cross-linking reactions as well as with ATPase activity changes.
通过交联反应、ATP酶活性、盐溶解性和40%饱和硫酸铵（AS）提取率，研究了暴露于非酶促羟基自由基生成系统（HRGS）的鸡肌原纤维中肌球蛋白的生化变化。用HRGS处理肌原纤维会导致肌球蛋白重链（MHC）通过二硫键交联，Ca-ATP酶活性增加，K-ATP酶活性降低，这表明包括活性位点处的肌球蛋白巯基被修饰。具体变化取决于HRGS中H₂O₂的浓度以及H₂O₂与肌原纤维的重量比。另一方面，与MHC的交联反应相比，HRGS处理样品中肌球蛋白的盐溶解性或AS提取率的降低进展缓慢，这表明相当数量的肌球蛋白生物聚合物在离子溶液中仍保持亲水性。结果表明，MHC的初始交联发生在肌球蛋白分子内部，随后通过分子间交联使肌球蛋白分子逐渐聚集。在当前实验条件下的氧化降低了肌原纤维蛋白的凝胶形成能力，这与分子内和分子间交联反应的进展以及ATP酶活性变化相一致。
