Norde W, Zoungrana T
Department of Physical Chemistry and Colloid Science, Wageningen Agricultural University, POB 8038, 6700 EK, Wageningen, The Netherlands.
Biotechnol Appl Biochem. 1998 Oct;28(2):133-43.
A proteolytic enzyme, alpha-chymotrypsin, and a lipolytic enzyme, cutinase, were adsorbed from aqueous solutions on solid surfaces with different hydrophobicities and morphologies. With both enzymes the affinity of adsorption is larger for the more hydrophobic surface. Water-soluble, flexible oligomers grafted on the sorbent surface cause a decrease in enzyme adsorption. CD spectroscopy and differential scanning calorimetry (DSC) indicate severe structural perturbations in the enzymes resulting from adsorption. The CD spectra reflect an average of the structure of the whole protein population. The DSC data allow additional conclusions to be drawn on the heterogeneity in the conformational states of the adsorbed enzymes. The degree of structural perturbation, that is the fraction of the adsorbed molecules of which the structure is perturbed, is lower at a surface that (1) is less hydrophobic, (2) contains water-soluble flexible oligomers and (3) is more covered by the protein. The specific activities of the enzymes are decreased on adsorption, more or less following the extent of structural perturbation. Unlike in solution, in the adsorbed state the heat-induced inactivation process is not identical with the heat-induced unfolding process. Furthermore, when the enzymes are adsorbed their specific activities are much less sensitive to temperature variation.
一种蛋白水解酶α-胰凝乳蛋白酶和一种脂肪分解酶角质酶，从水溶液中吸附到具有不同疏水性和形态的固体表面上。对于这两种酶，疏水性越强的表面吸附亲和力越大。接枝在吸附剂表面的水溶性柔性低聚物会导致酶吸附量下降。圆二色光谱（CD）和差示扫描量热法（DSC）表明，吸附导致酶的结构发生严重扰动。CD光谱反映了整个蛋白质群体结构的平均值。DSC数据有助于就吸附酶构象状态的异质性得出更多结论。在以下表面上，结构扰动程度（即结构受到扰动的吸附分子的比例）较低：（1）疏水性较弱；（2）含有水溶性柔性低聚物；（3）被蛋白质覆盖程度较高。酶的比活性在吸附时降低，或多或少与结构扰动程度相关。与在溶液中不同，在吸附状态下，热诱导失活过程与热诱导展开过程不同。此外，当酶被吸附时，它们的比活性对温度变化的敏感性要小得多。
