Yoshimoto Makoto, Miyazaki Yuya, Kudo Yoshiyuki, Fukunaga Kimitoshi, Nakao Katsumi
Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Japan.
Biotechnol Prog. 2006 May-Jun;22(3):704-9. doi: 10.1021/bp050416m.
A catalase-containing liposome (CAL) was prepared and characterized in terms of stability during storage and catalysis of the decomposition of hydrogen peroxide (H2O2) that was initially added or produced in the oxidation of glucose catalyzed by the glucose oxidase-containing liposomes (GOL). The reactors used were a test tube and an external loop airlift bubble column as the static liquid and circulating liquid flow systems, respectively. The free catalase (CA) at low concentrations was unstable during storage at 4 degrees C as a result of dissociation of the tetrameric CA subunits. On the other hand, the deactivation of the CA activity in the CAL was depressed because of the high CA concentration in the CAL liposome. The CAL effectively catalyzed the repeated decompositions at 25 degrees C with 10 mM H2O2 added initially, whereas the free CA was significantly deactivated during the repeated reactions. The high stability of the CAL was attributed to the moderately depressed reactivity, which was essentially derived from the diffusion limitation of the CAL membrane to H2O2 in the liquid bulk. In the GOL-catalyzed prolonged oxidation of 10 mM glucose at 40 degrees C in the static liquid in a test tube, both the free CA and CAL could continuously catalyze the decomposition of H2O2 produced. This was because the glucose oxidation rate was small due to the limited reactivity of the GOL to glucose with its low permeability through the GOL membrane. In the glucose oxidation catalyzed by the GOL with the free CA or the CAL in the airlift, much larger oxidation rates were observed compared to those in the test tube because the permeability of the GOL membrane to glucose was increased in the gas-liquid two phase flow in the airlift. The GOL/CAL system in the airlift operated in an acidic condition, which was preferable to the GO activity, gave the largest oxidation rate with negligible accumulation of the H2O2 produced. On the other hand, the GOL/free CA system gave an oxidation rate smaller than that of the GOL/CAL system even under the acidic condition due to an unfavorable interaction of the free CA molecules with the GOL membranes leading to the decreased reactivity of the GOL.
制备了一种含过氧化氢酶的脂质体（CAL），并从储存稳定性以及对最初添加的或在含葡萄糖氧化酶的脂质体（GOL）催化葡萄糖氧化过程中产生的过氧化氢（H2O2）分解的催化作用方面对其进行了表征。所使用的反应器分别为试管和外循环气升式鼓泡塔，作为静态液体和循环液体流动系统。低浓度的游离过氧化氢酶（CA）在4℃储存期间不稳定，这是由于四聚体CA亚基的解离。另一方面，由于CAL脂质体中CA浓度较高，CAL中CA活性的失活受到抑制。CAL在25℃下能有效地催化最初添加10 mM H2O2时的重复分解反应，而游离CA在重复反应过程中显著失活。CAL的高稳定性归因于反应活性适度降低，这主要源于CAL膜对液体主体中H2O2的扩散限制。在试管中40℃下GOL催化10 mM葡萄糖的长时间氧化反应中，游离CA和CAL都能持续催化产生的H2O2分解。这是因为GOL对葡萄糖的反应活性有限且其透过GOL膜的渗透率较低，导致葡萄糖氧化速率较小。在气升式反应器中，GOL与游离CA或CAL催化葡萄糖氧化时，与试管中的情况相比，观察到的氧化速率要大得多，这是因为在气升式反应器的气液两相流中，GOL膜对葡萄糖的渗透率增加。在气升式反应器中运行于酸性条件下（这对GO活性更有利）的GOL/CAL系统，产生的氧化速率最大，且产生的H2O2积累量可忽略不计。另一方面，即使在酸性条件下，GOL/游离CA系统的氧化速率也低于GOL/CAL系统，这是由于游离CA分子与GOL膜之间存在不利相互作用，导致GOL的反应活性降低。
