Gomez J E, Birnbaum E R, Royer G P, Darnall D W
Biochim Biophys Acta. 1977 Nov 25;495(1):177-82. doi: 10.1016/0005-2795(77)90252-5.
The effect of calcium ion on the urea denaturation of trypsin has been investigated. By using trypsin immobilized on glass beads, all possibilities of autolysis occurring during the denaturation process are eliminated. It was found that in 8 M urea calcium ion markedly decreases the denaturation rate of the immobilized trypsin. Conversely, the presence of calcium ion markedly accelerates the rate of renaturation of denatured immobilized trypsin. Calcium may exert its stabilizing effect on the tertiary structure of the protein by coordination to the side chains of Asp 194, Ser 190 and the carbonyl group of Ser 139 (using the chymotryptic numbering system).
研究了钙离子对胰蛋白酶尿素变性的影响。通过使用固定在玻璃珠上的胰蛋白酶，消除了变性过程中发生自溶的所有可能性。结果发现，在8M尿素中，钙离子显著降低了固定化胰蛋白酶的变性速率。相反，钙离子的存在显著加速了变性固定化胰蛋白酶的复性速率。钙可能通过与天冬氨酸194、丝氨酸190的侧链以及丝氨酸139的羰基（使用胰凝乳蛋白酶编号系统）配位，对蛋白质的三级结构发挥稳定作用。
