肉牛宰后初期一磷酸腺苷活化蛋白激酶活性在不同部位肉中的差异表达及与牛肉品质关系

文中主要探讨了一磷酸腺苷活化蛋白激酶(adenosine monophosphate-activated proteinkinase,AMPK)在宰后早期(3、5.5、7和10 h)不同部位牛肉中的差异性表达以及对最终牛肉品质的影响。选取牛柳(psoas major,PM)与西冷(longissimus dorsi,LD)2个部位,分别测定p H值、AMPK活性、糖酵解指标和肉品质指标。研究结果表明:随着宰后时间的延长,AMPK的活性显著下降(P0.05),而且PM中的AMPK活性显著高于LD(P0.05);AMPK活性与p H值与肌糖原含量呈显著正相关,与乳酸含量及(AMP+IMP)/ATP[AMP:adenosine monophosphate,一磷酶腺苷;IMP:inosine monophosphate,肌苷酶;ATP:adehosine triphosphate,三磷酶腺苷)呈显著负相关关系(P0.05),丙酮酸激酶随宰后时间先升高后降低(P0.05),而且PM中丙酮酸激酶达到最大活性值的时间以及最大值要早于且高于LD(P0.05);同时,PM在成熟期间表现出较高的嫩度以及较低的蒸煮损失(P0.05)。上述结果表明,AMPK能够通过调节糖酵解进程而影响牛肉的品质。     

不同预冷时间下鮰鱼能量代谢和加工品质的相关性分析

为了研究不同预冷时间下淡水鱼能量代谢和加工品质的相关性,本实验以鮰鱼为研究对象,分别测定了鮰鱼宰杀后在4℃下预冷48 h内的能量物质(糖原、乳酸、三磷酸腺苷(adenosine-5’-triphosphate,ATP)及其关联物含量)、代谢酶(己糖激酶(hexokinase,HK)、丙酮酸激酶(pyruvate kinase,PK)、乳酸脱氢酶(lactate dehydrogenase,LDH)、肌酸激酶(creatine kinase,CK))活力、理化品质(pH值、蒸煮损失率、加压失水率、质构特性、K值、色泽)变化。结果表明:随着预冷时间的延长,鮰鱼中糖原和乳酸含量在24 h内不断下降,随后开始积累;二磷酸腺苷、一磷酸腺苷、肌苷酸含量逐渐降低,次黄嘌呤、肌苷含量逐渐升高,ATP几乎检测不到;HK活力不断下降,PK活力在预冷8 h后上升至最大值,随后不断下降,LDH及CK活力均呈波动式下降;pH值和剪切力逐渐下降;加压失水率、蒸煮损失率以及色泽在24 h内保持稳定,在48 h后显著上升(P0.05),鱼肉的持水性下降;K值不断上升,并在24 h内保持在20%的高鲜度范围内。通过相关性分析发现:糖原含量和乳酸含量呈显著正相关(P0.05);K值与HK活力呈显著负相关(P0.05),与白度呈极显著正相关(P0.01);LDH活力与CK活力、剪切力呈显著正相关,与白度呈显著负相关(P0.05);加压失水率与蒸煮损失率呈显著正相关(P0.05)。宰后鮰鱼在预冷24 h内更有利于其在加工过程中的品质控制。     

乙醇胁迫对乳酸杆菌关键酶活力的影响

分别以面包乳杆菌(Lactobacillus crustorum D2-5)和植物乳杆菌(Lactobacillus plantarum D5-5)为研究对象,进行不同乙醇体积分数胁迫后菌体活力的对比,测定了乙醇胁迫后菌体中己糖激酶(HK)、丙酮酸激酶(PK)、乳酸脱氢酶(LDH)及ATP酶的活力变化,分析了乙醇胁迫后造成菌体失活的主要因素。结果表明:5%乙醇胁迫处理有助于提高菌体存活率,但是效果不显著;8%乙醇胁迫后的菌体存活率明显降低,面包乳杆菌D2-5和植物乳杆菌D5-5存活率依次仅为26.61%和23.50%,菌体的生长受到严重抑制,致使相关酶活力降低。乙醇胁迫对乳酸杆菌己糖激酶影响不显著,对其丙酮酸激酶、乳酸脱氢酶及ATP酶具有极显著的影响。这一结果说明,丙酮酸激酶、乳酸脱氢酶及ATP酶是影响乙醇胁迫损失的关键酶,酶活力变化与菌体活力相关。     

AMPK活化调控的能量代谢对宰后牦牛肉肉色稳定性影响的研究

为探究牦牛肉在宰后成熟过程中单磷酸腺苷激活蛋白激酶（AMPK）活化调控的能量代谢对肉色稳定性的影响,本实验以牦牛背最长肌为研究对象,使用AMPK激活剂（AICAR）和抑制剂（Compound C）对其进行处理,并置于4 ℃下成熟,在相应的成熟时间点对AMPK活性、肉色及能量代谢相关指标进行测定,并进行肉色和能量代谢指标相关性分析。结果表明:成熟至12 h,与对照组相比,AICAR组AMPK活力提高了13.17%,而抑制组降低了9.03%,表明AICAR对AMPK活性有激活作用,而Compound C对AMPK活性有明显的抑制作用。随着成熟时间的延长,三者的L*值、a*值和己糖激酶的活性均呈先上升后下降趋势,b*值、H*值、乳酸含量均呈逐渐上升的趋势,其中L*值、b*值和H*值始终为AICAR组>对照组>Compound C组,a*值始终为AICAR组<对照组相似文献   

不同月龄和部位羊肉中一磷酸腺苷激活蛋白激酶活性与肉品质的关系

选取巴美肉羊5、6、8 月龄和12 月龄不同部位的骨骼肌,分别测定并比较它们的一磷酸腺苷激活蛋白激酶（AMP-activated protein kinase,AMPK）活性、糖酵解指标和肉质指标,以探讨AMPK与宰后肌肉品质的相关性。结果表明：AMPK活性随着月龄的增加呈下降的趋势（P＜0.05）,背最长肌的AMPK活性显著高于股二头肌和臂三头肌（P＜0.05）;AMPK活性与肌糖原含量、乳酸含量和己糖激酶活性呈极显著正相关（P＜0.01）,与b*值呈显著负相关（P＜0.05）,与L*值、a*值、剪切力和熟肉率呈负相关（P＜0.05）。提示AMPK活性与肌糖原、己糖激酶、乳酸、肉的色泽、剪切力和熟肉率具有相关性,AMPK可能通过调节糖酵解进程进而影响肉品质。     

蛋白质组学揭示宰前温和驱赶改善猪肉品质的潜在机制

宰前不同驱赶方式对生猪造成不同程度应激,进而影响猪肉品质。本实验以45头6月龄大的生猪为研究对象,随机分配到完全温和驱赶组(全温组,n=15)、声音温和驱赶组(声温组,n=15)和传统驱赶组(传统组,n=15)。宰后测定生猪血液应激指标、肌肉品质和理化指标,并利用蛋白质组学鉴定影响宰后肌肉能量代谢与肉品品质的调控蛋白,探索宰前驱赶影响肉品品质的潜在机制。结果表明:相比于传统组,全温组的肌酸激酶、乳酸脱氢酶、皮质醇含量显著下降(P0.05),应激程度最低;红度a*值显著升高(P0.05),蒸煮损失率显著降低(P0.05),PSE(pale, soft, exudative)肉发生率下降;宰后45 min和3 h的pH值显著提高(P0.05);宰后45 min和3 h的ATP含量显著增大(P0.05)。相似地,声温组应激水平也低于传统组,其肌酸激酶、乳酸脱氢酶活力、45 min和3 h的pH值、45 min和3 h的ATP含量等指标都处于中间水平。此外,蛋白质组学鉴定出46个差异蛋白,包括能量代谢相关的ATP依赖性6-磷酸果糖激酶、α-1,4-葡聚糖磷酸化酶、糖原脱支酶、甘油醛-3-磷酸脱氢酶、磷酸甘油酸激酶、异柠檬酸脱氢酶、线粒体肌酸激酶2以及肌肉收缩相关的肌球蛋白7。两组温和驱赶方式都减缓肌肉中的能量代谢进程并改变肌肉收缩状态,进而提高宰后肌肉pH值、糖原和ATP水平,最终改善猪肉品质。     

猪宰后不同部位白肌肉与正常肉品质变化、能量代谢的差异

对猪宰后不同部位白肌(pale soft exudative,PSE)肉与正常肉的品质变化及能量物质的代谢差异进行研究。选取"杜长大"阉公猪宰后背最长肌、股二头肌均为正常肉和PSE肉,测定不同时间点肉品质指标(pH值、离心失水率、剪切力、L*)及能量物质(糖原、腺苷三磷酸(adenosine triphosphate,ATP)、腺苷二磷酸、腺苷酸)含量的变化,并分析各自的相关性。结果表明:宰后2 h内,股二头肌ATP含量显著高于背最长肌(P0.05)。宰后8 h内所有样本ATP含量下降显著(P0.05);宰后48 h内,正常肉股二头肌糖原含量显著高于其他样本(P0.05);离心失水率变化和L*值变化呈正相关(P0.01);糖原含量和ATP含量的变化呈正相关(P0.01)。因此,股二头肌肉品质优于背最长肌,股二头肌的糖原、ATP含量高于背最长肌,背最长肌能量代谢速率高于股二头肌。     

乌珠穆沁羊与小尾寒羊一磷酸腺苷激活蛋白激酶酶活性与肉品质的关系研究

摘 要：目的 研究乌珠穆沁羊与小尾寒羊不同生长阶段、不同部位骨骼肌一磷酸腺苷激活蛋白激酶(adenosine monophosphate-activated protein kinase,AMPK)活性、糖酵解与肉质相关指标的内在变化规律。方法 通过夹心酶联免疫吸附法测定6月龄和8月龄乌珠穆沁羊与小尾寒羊的股二头肌、背最长肌与臂三头肌AMPK活性,比色法测定乳酸(lactic acid,LA)含量,微量法测定肌糖原含量和分光光度法测定己糖激酶(hexokinase,HK)含量以及常规法测定肉品质等相关性指标。结果 两个品种的肉羊之间AMPK活性无显著差异(P>0.05);AMPK活性升高同时pH24值、L*值、b*值与剪切力降低(P<0.05),LA、肌糖原含量、a*值和HK活性升高(P<0.05)。被激活的AMPK能够刺激产能过程糖酵解的HK活性、磷酸果糖激酶和丙酮酸激酶,酶活性与LA含量呈正相关,宰后呼吸方式的改变导致pH快速下降剪切力增大,嫩度与熟肉率降低。结论 表明宰后羊肉AMPK活性与糖酵解和肉品质之间存在一定的影响。AMPK活性以及糖酵解的程度不同,可能导致了肉的剪切力、瘦肉率以及嫩度等差异,AMPK活性增强糖酵解的关键酶被激活活性增加,加快糖酵解进程从而影响肉品质。     

冷冻干燥对乳酸菌代谢活力的影响

以保加利亚乳杆菌和植物乳杆菌ST-Ⅲ为研究对象,用15%蔗糖、10%海藻糖、15%蔗糖＋2%谷氨酸钠及10%脱脂乳为冷冻保护剂,与不加冷冻保护剂的样品进行冻干后菌种活力的对比,测定冷冻干燥后菌体中己糖激酶、丙酮酸激酶、乳酸脱氢酶的活力,胞外蛋白及胞内Ca2＋的浓度变化。结果表明：冷冻干燥对菌体的己糖激酶和丙酮酸激酶影响不显著,对乳酸脱氢酶具有显著性的影响。同时,不加保护剂菌体的胞外蛋白含量明显高于添加保护剂的,而胞内Ca2＋却远低于其他组。这一结果说明,冷冻干燥使代谢关键酶如乳酸脱氢酶失活,同时对细胞膜造成了损伤,从而引起细胞代谢活力的下降。     

不同月龄和部位乌珠穆沁羊AMPK活性与肉品质的关系

为研究乌珠穆沁羊不同生长阶段、不同骨骼肌一磷酸腺苷激活蛋白激酶（adenosine monophosphate-activated proteinkinase,AMPK）活性、糖酵解相关指标和肉质相关指标的内在变化规律,选取3、6、9月龄乌珠穆沁羊背最长肌、股二头肌和腰大肌,分别测定其AMPK活性、肌糖原含量、乳酸含量、己糖激酶（hexokinase,HK）活性、pH值、剪切力和色泽等指标。结果表明：AMPK活性升高时pH24 h值、红度值（a*）明显下降,并呈显著负相关（P<0.05）;剪切力随着月龄增大而降低（P<0.05）,腰大肌黄度值（b*）最大,背最长肌b*最小,腰大肌a*变化规律与b*相同,股二头肌与背最长肌a*变化规律与b*相反;同一部位肌糖原含量与月龄呈显著正相关（P<0.05）,背最长肌最大,股二头肌最小（P<0.05）,乳酸含量变化规律与肌糖原含量总体相同;HK活性与月龄呈正相关（P<0.05）,腰大肌最大,股二头肌最小（P<0.05）,AMPK活性随着b*、肌糖原总体含量、6月龄与9月龄乳酸和HK活性升高呈现显著上升趋势（P&l...     

AMPK活性对宰后牛肉糖酵解、肌肉内环境及品质的影响

为探究牛肉宰后成熟过程中单磷酸腺苷活化蛋白激酶（adenosine monophosphate-activated protein kinase,AMPK）对糖酵解、肌肉内环境及品质的影响,以0.50 mol/L 5-氨基咪唑-4-甲酰胺核苷（5-amino-4-imidazolecarboxamide,AICAR）处理的西杂牛背最长肌为对象,于4 ℃进行成熟,测定宰后成熟期间肌肉AMPKα基因（PRKAA1、PRKAA2）转录量、P-AMPK表达量、AMPK活性、糖酵解水平及品质指标的变化情况。结果表明：宰后24～120?h,处理组AMPKα基因转录量、P-AMPK表达量及AMPK活力均显著高于对照组（P＜0.05）;72～168?h,处理组pH值和肌糖原含量显著低于对照组（P＜0.05）,乳酸含量显著高于对照组（P＜0.05）;12～168?h,处理组L*、b*值及ATP、ADP、AMP和IMP含量均显著高于对照组（P＜0.05）,a*值显著低于对照组（P＜0.05）;24～120?h,处理组蒸煮损失率和肌原纤维小片化指数显著高于对照组（P＜0.05）,剪切力显著低于对照组（P＜0.05）。AICAR通过激活AMPK并加快宰后糖酵解影响肌肉内环境、肉色、剪切力及肌纤维微观结构变化,加快宰后肌肉成熟进程,说明AMPK活性对宰后肌肉糖酵解及品质变化具有重要影响,且可通过调控宰后肌肉AMPK活性来调节肌肉品质。     

Effects of pithing on pH, creatine phosphate and ATP-related compounds of beef Psoas major and Longissimus dorsi muscles

The effects of pithing at slaughter on meat quality were studied in M. longissimus dorsi (LD muscle) and M. psoas major (PM muscle) from steers. Ten steers, half of them pithed and the others not pithed at slaughter, were used for determining pH values and concentrations of creatine phosphate (CP), adenosine triphosphate (ATP) and its breakdown products in the muscles at 2·0 h post mortem. CP was not detected in any PM muscles from pithed steers and no significant differences were observed between pithed and non-pithed steers on the mean values of pH and any compounds, but significant differences were observed in the variance of pH value, ATP, (inosine monophosphate IMP) and inosine levels in PM muscles and of (adenosine diphosphate ADP) and IMP levels in LD muscles. When two steers with excitable temperament were excluded from the pithed group significant differences of variance between the treatments were observed only in PM muscles. The pithing procedure thus affects the levels of pH and of some of the ATP-related compounds in the PM but not in LD muscles.     

Early Postmortem Detection of Exudative Pork Meat Based on Nucleotide Content

The content of nucleotide metabolites in the muscle L. dorsi was analyzed for the detection of pale, soft and exudative (PSE) pork meats at just 2 h postmortem. PSE meat was characterized by significantly lower (p < 0.05) amounts of adenosine 5'-triphosphate (ATP) and higher adenosine 5'-monophosphate (AMP), inosine 5'-monophosphate (IMP), inosine (ino) and hypoxanthine (hyp) than normal meat. IMP and ino classified all the samples from both groups with statistical significance (p < 0.05). The K₀ value, R' value and IMP/ATP ratios were also useful indicators for full distinction of PSE meats. Thus, the assay of any of these nucleotide metabolites may allow a good detection of PSE meats at very short, only 2 h, postmortem time.     

Hydrophilic interaction chromatographic determination of adenosine triphosphate and its metabolites

A new HPLC method based on hydrophilic interaction chromatography (HILIC) has been developed for the simultaneous analysis of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine (Ino), hypoxanthine (Hx) and nicotinamide adenine dinucleotide (NAD⁺) in pork loin muscle. The chromatographic analysis has been developed using a zwitterionic polymeric column and it has been optimised in terms of linearity, repeatability, reproducibility and recovery. Detection limit values of 0.10, 0.15, 0.05, 0.16, 0.16, 1.72 and 0.15 μg/mL for ATP, ADP, AMP, IMP, Ino, Hx and NAD⁺ respectively were achieved. A comparison between the pork meat concentrations of the compounds analysed by hydrophilic interaction chromatography (HILIC), using a ZIC®-pHILIC column, and ion-pair reversed-phase chromatography (IP-RP-HPLC), using a Zorbax Eclipse XDB-C18 column, has been done, concluding that the new chromatographic methodology constitutes a valid and reliable alternative to the existing methods. Finally, this method has also proved to be very effective in the isolation of guanosine, guanosine monophosphate (GMP), guanosine diphosphate (GDP), guanosine triphosphate (GTP), creatinine (Cn) and uric acid (UA) from a standards mixture.     

Effects of meat quality and storage on the breakdown of adenosine triphosphate in muscle from swine

The quality of pork is dependent on animal genotype, pre-slaughter handling, processing, maturation, and storage. We investigated the pattern of adenosine triphosphate (ATP) breakdown as it related to these factors. Samples of the thoracis portion of the longissimus dorsi muscle were obtained from 19 randomly selected German Landrace-Pietrain crossbreed swine. Based on their 40 min post-mortem pH and electrical conductances, three groups were classified: (1) PSE meat, pH ≤ 5·6 and conductance >10 mS (n = 7); (2) intermediate quality, pH 5·6-6·0 and conductance between 4 and 10 mS (n = 5); and (3) normal quality, pH ≥ 6·0 and conductance < mS (n = 7). Hence, the animals investigated included those susceptible to malignant hyperthermia (porcine stress-syndrome). Twenty-four hours post mortem samples were evaluated for the following parameters: ATP metabolism, pH values, electrical conductance, meat colour, water binding capacity, shear force and general composition (i.e. total protein, fat, mineral and water contents). Muscle composition was the same in each group, but for the other parameters there were clear differences. Following different storage periods and conditions (1 or 5 days at 4°C and 27 days at -18°C), the degree of ATP metabolism as well as general meat quality (i.e. including sensory evaluation) were reassessed. Samples from the pre-selected groups became less discernible following prolonged storage. In all animals, the pattern of ATP breakdown was similar, the major metabolites including inosine monophosphate, hypoxanthine, adenosine monophosphate, and inosine. The degree of breakdown was dependent on the duration and temperature of storage, but not on animal type. The muscular samples for the intermediate and normal muscle groups, which were stored for 27 days at -18°C, were given the highest sensory evaluation scores. The simple HPLC measurement of ATP metabolism was considered as a useful means to assess appropriate storage.     

Extractive components of boiled–dried scallop adductor muscle and effect on the taste of soup after mixing with chicken leg meat

The extractive components of raw and boiled–dried scallop adductor muscle were examined. On a dry weight basis the levels of total free amino acids, total adenosine triphosphate (ATP) and related compounds, and betaines in the boiled–dried sample were lower than those in the raw muscle, which may have been due to the outflow of these compounds during boiling. Soup prepared from the boiled–dried scallop and chicken leg meat was assessed by sensory evaluation. This soup cooked with the scallop and chicken was stronger in sweetness, umami and body and rated higher in overall preference than the soup containing these ingredients after cooking separately. The inosine monophosphate (IMP) level in the former soup was 4.4 times higher than that in the latter. The adenosine monophosphate (AMP) deaminase (EC 3.5.4.6) activity in the crude extract from the chicken meat was 9.16 units l^?1, whereas no activity could be detected in the crude extract from the boiled–dried scallop. It is concluded that AMP, which was mainly derived from the boiled–dried scallop, was converted to IMP by AMP deaminase from the chicken meat during the preparation of the soup, resulting in an improvement in the taste. Copyright © 2004 Society of Chemical Industry