虾夷扇贝闭壳肌和外套膜肌原纤维蛋白的特性分析

为探索采捕后活品虾夷扇贝品质变化与其肌肉蛋白质生理特性变化间的关联,本研究以虾夷扇贝2个可食部肌肉为研究对象,以肌原纤维蛋白ATPase活性为指标(Ca²⁺-ATPase,Mg²⁺-ATPase),对扇贝肌原纤维蛋白(Mf)的稳定性进行了系统探索。首先,分别提取闭壳肌肌原纤维(A-Mf)和外套膜肌原纤维(M-Mf);然后,考察了不同因素(离子强度I、pH、温度)对Mf的ATPase活性的影响规律;对A-Mf及M-Mf的稳定性进行了探索;进一步比较了闭壳肌和外套膜肌原纤维蛋白ATPase的失活特性。研究结果表明:(1)虾夷扇贝闭壳肌与外套膜的Mf的理化性质相似,A-Mf与M-Mf的pI均在5.0附近,粘度分析发现A-Mf热稳定性高于M-Mf。(2)ATPase活性变化规律的结果发现,与脊椎动物中的鱼类一样,作为无脊椎动物的扇贝,与Mg²⁺-ATPase相比,Ca²⁺-ATPase更能准确地反映Mf的稳定性。(3)闭壳肌和外套膜二者的Mf的Ca²⁺-ATPase呈现出共同特性,在pH为中性时活性最高;A-Mf与M-Mf的差异性则表现为前者的Ca²⁺-ATPase在较低离子强度(I=0.2)下活性最高,后者则在较高离子强度(I=0.5)下活性最高;离子强度对A-Mf的热稳定性影响不明显,而M-Mf的热稳定性明显受到离子强度的影响,其在较低离子强度下表现出更好的稳定性。(4)Ca²⁺-ATPase失活速率的研究发现,无论是闭壳肌还是外套膜,其稳定性与离子强度I和温度均呈现显著正相关(R²=0.8181、0.8436和R²=0.9887、0.9557);二者在pH 7.0左右的稳定性最好,偏离中性会促使Ca²⁺-ATPase失活,与碱性条件相比,酸性对蛋白质稳定性的破坏更加明显。

Characteristics of the adductor and mantle myofibrils from Patinopecten yessoensis

To explore the correlation between the mechanism changes in texture quality of post-harvested commercial bivalve molluscs and the physiological properties changes of muscle protein,a trial study of scallop (Patinopecten yessoensis) edible muscles was carried out focusing on myofibrillar (Mf) protein,and ATPase activities were taken as indicators to explore the stability of myofibrillar protein extracted from adductor (A-Mf) and mantle (M-Mf).Comparisons and analysis between the extracted Mfs from adductor muscle and mantle were made,including the solubility,viscosity,the influences of I,pH and temperature on the ATPase stability of Mfs,and their ATPase inactivation characteristics.The results showed that:(1) A-Mf and M-Mf presented similarity in solubility and both pI appeared around 5.Viscosity analysis showed that the thermal stability of A-Mf was higher than that of M-Mf.(2) Compared with Mg²⁺-ATPase,Ca²⁺-ATPase can more accurately indicate the stability of A-Mf and M-Mf which was the same as vertebrate fishes.(3) The Ca²⁺-ATPase activities of adductor and mantle Mfs had the common characteristics,for example,the highest activity was in the neutral pH;the difference between A-Mf and M-Mf was that the highest Ca²⁺-ATPase activity of the former was at low ionic strength (I=0.2) whereas the latter was at high ionic strength (I=0.5);the influence of ionic strength on the A-Mf was not obvious whereas M-Mf was affected by the ionic strength obviously which showed the better stability at low ionic strength.(4) The inactivation characteristics of Ca²⁺-ATPase showed that both the adductor and mantle Mfs had a significant correlation (R²=0.818 1,0.843 6 and R²= 0.9887,0.9557) with the ionic strength and temperature,the best stability of A-Mf and M-Mf were in the range of pH 7.0,and acid conditions damaged Ca²⁺-ATPase activity more obviously than alkaline conditions.