Leaver J, Dalgleish D G
Hannah Research Institute, Ayr, Scotland, U.K.
Biochim Biophys Acta. 1990 Dec 5;1041(3):217-22. doi: 10.1016/0167-4838(90)90275-k.
The topography of bovine beta-casein at a soya oil/water interface was studied by following the kinetics of the trypsin-catalysed hydrolysis. Tryptic peptides were identified from their amino acid compositions and the kinetics were compared with those obtained from beta-casein in solution. Whereas soluble beta-casein was initially hydrolysed at a number of trypsin-sensitive bonds, the hydrolysis of the protein at the interface was a more ordered event. The crucial initiating step was the cleavage of the N-terminal peptides 1-25 and 1-28 from the molecule. Hydrolysis at other trypsin-sensitive sites could then occur. This suggests that with the exception of the large hydrophilic moiety in the N-terminal region, most of the beta-casein molecule is inaccessible to the proteinase, and lies fairly flat on the oil/water interface. After removal of the N-terminal peptide, the remaining macropeptide can reorientate and other hydrophilic regions become accessible to the proteinase.
通过跟踪胰蛋白酶催化水解的动力学，研究了大豆油/水界面处牛β-酪蛋白的拓扑结构。根据胰蛋白酶水解肽的氨基酸组成对其进行鉴定，并将动力学与溶液中β-酪蛋白的动力学进行比较。可溶性β-酪蛋白最初在多个对胰蛋白酶敏感的键处发生水解，而界面处蛋白质的水解是一个更有序的过程。关键的起始步骤是从分子中切割出N端肽1-25和1-28。然后可以在其他对胰蛋白酶敏感的位点发生水解。这表明，除了N端区域的大亲水部分外，β-酪蛋白分子的大部分对蛋白酶是不可接近的，并且相当平坦地位于油/水界面上。去除N端肽后，剩余的大肽可以重新定向，其他亲水区域变得可被蛋白酶接近。
