宰后早期猪肉、牛肉和鸡肉中能量代谢及蛋白质磷酸化张爽1,2，张楠2,*，朱良齐2，李春保2（1.芜湖职业技术学院，安徽芜湖 241003；2.南京农业大学食品科技学院，江苏南京 210095）摘 要：目的：探讨畜禽肉宰后能量代谢的差异及其可能的原因。
方法：于宰后45 min测定鸡肉、灰白（pale soft exudative，PSE）猪肉、正常猪肉和牛肉中糖原、ATP/ADP/AMP含量及乳酸脱氢酶（lactate dehydrogenase，LDH）活性，并提取肌浆和肌原纤维蛋白进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate- polyacrylamide gel electrophoresis，SDS-PAGE）和液相色谱-串联质谱鉴定，分析各组肉的磷酸化水平差异。
结果：牛肉中糖原含量显著高于其他组（P＜0.05），正常猪肉组糖原和ATP含量显著高于PSE猪肉组和鸡肉组（P＜0.05），而PSE猪肉组的LDH活性显著高于其他组（P＜0.05）；肌浆蛋白SDS-PAGE ProQ染色表明，宰后45 min PSE猪肉组中6 个条带的磷酸化水平显著低于正常猪肉组（P＜0.05），而另有6 个条带的磷酸化水平显著高于正常猪肉组（P＜0.05）。
牛肉组和鸡肉组中分别有3 个和1 个条带的磷酸化水平偏低，1 个条带和8 个条带的磷酸化水平明显偏高。
而肌原纤维蛋白电泳表明，牛肉中大部分蛋白质的磷酸化水平处于最高值，而鸡肉组处于最低值，猪肉介于两者之间；PSE猪肉组中7 个条带的磷酸化水平显著低于正常猪肉（P＜0.05）；6 个条带的磷酸化水平显著高于正常猪肉（P＜0.05）。
结论：宰后异质肉的形成受宰后糖原和ATP消耗速率、LDH活性的影响，同时与肌肉中糖酵解酶的磷酸化水平有关。
关键词：异质肉；乳酸脱氢酶；糖酵解；能量代谢Energy Metabolism and Protein Phosphorylation of Pork, Beef and Chicken during the Early Postmortem PeriodZHANG Shuang1,2, ZHANG Nan2,*, ZHU Liangqi2, LI Chunbao2(1. Wuhu Institute of Technology, Wuhu 241003, China;2. College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China)Abstract: Objective: To explore the major cause for abnormal meat. Methods: At 45 min postmortem, chicken, pale soft exudative (PSE) pork, normal pork and beef were taken for the analysis of glycogen, ATP/ADP/AMP contents, lactate dehydrogenase (LDH) activity. At the same time, myofibrillar and sarcoplasmic proteins were extracted and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the bands of interest were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The difference in band intensity was evaluated. Results: Glycogen was higher in beef than three other meats (P < 0.05). Glycogen and ATP contents were higher in PSE pork than normal pork and chicken (P < 0.05). LDH activity in PSE pork was much higher than all other groups (P < 0.05).SDS-PAGE with ProQ staining indicated that, at 45 min postmortem, the phosphorylation levels of sarcoplasmic proteins from 6 bands were lower in PSE pork than those of normal pork (P < 0.05), while sarcoplasmic proteins from other6 bands had higher phosphorylation levels than normal pork (P < 0.05). In addition, 3 bands in beef and 1 bands inchicken had lower phsophorylation levels, whilst higher phsophorylation levels were observed for 1 bands in beef and 8 bands in chicken. For myofibrillar proteins, the majority of bands in beef had highest phosphorylation levels, the lowest phosphorylation levels were found for chicken (P < 0.05), and pork was in the middle. Similarly, 7 bands in PSE pork had lower phosphorylation levels than normal pork (P < 0.05), while 6 bands had higher phosphorylation levels than normal pork收稿日期：2016-11-25基金项目：“十二五”国家科技支撑计划项目（2014BAD19B01）；江苏省农业自主创新项目（CX(15)1006）；国家现代农业（生猪）产业技术体系建设专项（CARS36-11）；南京农业大学基本业务费专项（KYCYL201502）；江苏省优势学科项目作者简介：张爽（1975—），女，副教授，硕士，研究方向为食品加工与安全。
E-mail：goodluck_zs@*通信作者：张楠（1981—），男，博士研究生，研究方向为畜产品加工与质量控制。
E-mail：285913549@(P < 0.05). Conclusion: The rates of glycolysis and ATP depletion, and LDH activity had a great contribution to PSE pork, which is also associated with protein phosphorylation of glycolytic enzymes.Key words: abnormal meat; lactate dehydrogenase (LDH); glycolysis; energy metabolismDOI:10.7506/spkx1002-6630-201709012中图分类号：TS251.1 文献标志码：A 文章编号：1002-6630（2017）09-0072-07引文格式：张爽, 张楠, 朱良齐, 等. 宰后早期猪肉、牛肉和鸡肉中能量代谢及蛋白质磷酸化[J]. 食品科学, 2017, 38(9): 72-78. DOI:10.7506/spkx1002-6630-201709012. ZHANG Shuang, ZHANG Nan, ZHU Liangqi, et al. Energy metabolism and protein phosphorylation of pork, beef and chicken during the early postmortem period[J]. Food Science, 2017, 38(9): 72-78. (in Chinese with English abstract) DOI:10.7506/spkx1002-6630-201709012. 对异质猪肉发生率调查发现，灰白（p a l e s o f t exudative，PSE）猪肉发生率较高，黑干（dark firm dry，DFD）肉发生率较低。
相关文献显示，禽类中类PSE肉的发生率高达50%，而牛肉中DFD肉发生率较高，达到20%～30%左右[1-2]，说明异质肉的发生不仅受宰前因素的影响，同时可能与宰后肌肉糖酵解和能量代谢差异有关。
相比较而言，禽肉一般以冻肉消费或深加工为主，牛肉的核心问题是嫩度问题，对消费者的感官选择不会产生太大影响。
而PSE猪肉通常出现于冷鲜肉，其肉色苍白、汁液渗出、质地松软的特征直接影响消费者的购买行为，对产业效益的影响较大。
宰前应激容易导致异质肉的产生，而乳酸脱氢酶（lactate dehydrogenase，LDH）活性是反映机体能量代谢和心肌损伤的重要指标，LDH活性越高，PSE肉发生的可能性越高。
研究发现，糖酵解速率主要由ATP水解速率决定，它影响着糖酵解的第一步磷酸化反应和磷酸果糖激酶调控的反应，低浓度的ATP将促进这些反应，高浓度的ATP将阻止磷酸烯醇式丙酮酸转变成丙酮酸[3-5]。
ATP的大量消耗，导致糖酵解过程能量代谢加速，并导致宰后肌肉pH值快速下降[6-8]。
因此，宰后初期ATP浓度大小对糖酵解快慢及乳酸的生成起着重要作用。
肌肉中绝大多数酶都存在于肌浆中，而糖酵解酶又占到肌浆蛋白的2/3，糖酵解酶的活性是影响宰后肌肉pH值下降速率的主要因素，而糖酵解酶的活性又主要通过磷酸化水平来调控，研究发现宰后肌肉的糖原磷酸化酶、肌酸激酶、丙酮酸激酶等酶类的磷酸化变化能够调节肌肉能量代谢以及影响宰后pH值的下降速率。
