Moyano F J, Savoie L
Departo Biología Aplicada, Escuela Politécnica Superior, Universidad de Almería, 04120, Almería, Spain.
Comp Biochem Physiol A Mol Integr Physiol. 2001 Feb;128(2):359-68. doi: 10.1016/s1095-6433(00)00315-9.
Hydrolysis of three different proteins by either crude fish digestive extracts or purified mammal proteases was assayed using two different in vitro systems. The closed system was a modification of the pH-stat method including a previous acid digestion. The open system used a digestion cell containing a semi-permeable membrane which allowed continuous separation of the final products of hydrolysis with a molecular cut-off of 1000 Da. Assays in both systems resulted a similar arrangement of the tested proteins in relation to their ability to be hydrolyzed, with casein>fish meal> or =soybean meal. With the exception of casein, no significant differences were found between results produced by any of the enzyme sources using the closed system. In constrast, significantly higher hydrolysis of all proteins was produced by mammal enzymes under conditions operating in the open system. Differences in the rate of release of amino acids measured in this latter system were related both to the type of protein and the origin of the enzymes. When using purified mammal enzymes, release of lysine or phenylalanine from casein and soybean was high, but low from fishmeal. Isoleucine and valine present in fishmeal were preferentially hydrolyzed by commercial enzymes, but glycine and proline by fish enzymes.
使用两种不同的体外系统，测定了粗制鱼消化提取物或纯化的哺乳动物蛋白酶对三种不同蛋白质的水解情况。封闭系统是对pH计法的一种改进，包括之前的酸消化步骤。开放系统使用了一个含有半透膜的消化池，该半透膜允许连续分离水解终产物，其分子截留量为1000 Da。两个系统中的测定结果显示，就被水解的能力而言，受试蛋白质呈现出相似的排列顺序，即酪蛋白>鱼粉>或=豆粕。除酪蛋白外，使用封闭系统时，任何一种酶源产生的结果之间均未发现显著差异。相比之下，在开放系统的操作条件下，哺乳动物酶对所有蛋白质的水解程度显著更高。在后一种系统中测得的氨基酸释放速率差异既与蛋白质类型有关，也与酶的来源有关。当使用纯化的哺乳动物酶时，酪蛋白和豆粕中赖氨酸或苯丙氨酸的释放量较高，但鱼粉中的较低。鱼粉中存在的异亮氨酸和缬氨酸优先被商业酶水解，而甘氨酸和脯氨酸则被鱼酶水解。
