| dc.description.abstract | For last decades, the enzyme/biological immobilization has been widely applied for industry such as textile, beverage, and food etc. However, it is unclear why the embedded enzyme still retain its biological activity. Regarding our previous publication in 2015, a de novo approach was used to encapsulate the enzyme into metal-organic frameworks (MOFs) crystals and able to maintain bioactivity of enzymes. In order to further study of biocomposite by using de novo approach as a model, this work is focusing on the effects of embedded enzyme activities under enzyme-unfriendly environment.
With a series of examinations, we found the enzyme is able to maintain its biological function under a wider range of conditions after being embedded in MOF microcrystals via a de novo approach. We suggest the enhancement of stability arise from confinement of enzyme molecules in the mesoporous cavities in the MOFs, which reduces the structural mobility of enzyme molecules. Additionally, we embedded catalase (CAT) into zeolitic imidazolate frameworks-90/8 (ZIF-90 and ZIF-8), and then exposed both embedded CAT and free CAT to a denature reagent, i.e., urea, and high temperatures, i.e., 80 °C. The embedded CAT still maintains the decomposition ability of hydrogen peroxide with apparent rate constants kobs (s−1) of 1.30 × 10−3 and 1.05 × 10−3 even when exposed to 6 M urea and 80 °C, respectively, in contrast, free CAT shows undetectable activity. A fluorescence spectroscopy study also had shown that the structure conformational change of the embedded CAT is lesser than it of free CAT as incubated in denaturing condition. Therefore, the result of this work indicated that the biological activity of embedded enzyme is still maintained under the harsh environment.
Finally, this work agreed with our hypothesis that not only biocomposites can shield embedded enzyme against structural unfolding, but also explore the mechanism of enzyme inactivation by the use of nanoporous MOFs as well as create a novel model for probing physiological mechanism of biomolecules.
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