Physikalische Chemie I, University of Bayreuth, 95440, Bayreuth, Germany.
J Phys Chem B. 2009 Dec 10;113(49):16039-45. doi: 10.1021/jp907508w.
We present a quantitative study of the catalytic activity of beta-d-glucosidase from almonds adsorbed on thermosensitive microgels. The core-shell particles used as a carrier system consist of a solid polystyrene core onto which a poly(N-isopropylacrylamide) (PNiPA) network is grafted. In the swollen state of this microgel, i.e., below the critical solution temperature (LCST) of PNiPA, high amounts of enzyme can be immobilized into the PNiPA network without loss of colloidal stability. The enzymatic activity of beta-d-glucosidase in its native form and in the adsorbed state was analyzed in terms of Michaelis-Menten kinetics. Moreover, the dependence of the enzymatic activity on temperature was investigated. We demonstrate that the enzymatic activity of beta-d-glucosidase adsorbed on such a core-shell microgel is increased by a factor of more than three compared to its activity in solution. This is in marked contrast to other carrier systems that usually lead to a strong decrease of enzymatic activity. Both the high loading capacity of the carrier observed and the increase of the catalytic activity of immobilized beta-d-glucosidase are traced back to the formation of strong interactions between the enzyme and microgel. Studies by Fourier-transform infrared (FT-IR) spectroscopy identify the formation of hydrogen bonds as driving forces for the adsorption. Hydrogen bonding may also be the reason for the enhanced activity.
我们对杏仁中β-葡萄糖苷酶在热敏性微凝胶上的催化活性进行了定量研究。所使用的核壳颗粒作为载体系统，由固体聚苯乙烯核组成，其上接枝有聚（N-异丙基丙烯酰胺）（PNiPA）网络。在这种微凝胶的溶胀状态下，即 PNiPA 的临界溶液温度（LCST）以下，可以将大量的酶固定到 PNiPA 网络中而不会损失胶体稳定性。我们根据米氏动力学分析了β-葡萄糖苷酶在其天然形式和吸附状态下的酶活性。此外，还研究了酶活性对温度的依赖性。我们证明，与在溶液中的活性相比，吸附在这种核壳微凝胶上的β-葡萄糖苷酶的酶活性增加了三倍以上。这与通常导致酶活性大幅下降的其他载体系统形成鲜明对比。载体的高负载能力以及固定化β-葡萄糖苷酶的催化活性的提高都可以归因于酶与微凝胶之间形成的强相互作用。傅里叶变换红外（FT-IR）光谱研究表明氢键的形成是吸附的驱动力。氢键也可能是提高活性的原因。
