A team of researchers led by NDSU assistant professors Zhongyu Yang in chemistry and biochemistry and Bingcan Chen in plant sciences has recently published two articles focused on the development of metal-organic materials that can successfully immobilize enzymes and the introduction of a unique method to characterize the structural basis governing the catalytic performance of the entrapped enzymes.
The back-to-back papers are published in the premiere issue of Chem Catalysis, a new premier journal from Cell Press that covers research on fundamental and applied catalysis.
Yang and Chen’s research team includes NDSU postdoctoral research fellows Yanxiong Pan (chemistry and biochemistry) and Hui Li (plant sciences); chemistry and biochemistry research assistants Jasmin Farmakes, Qiaobin Li, and Mary Lenertz; and collaborators from Purdue University and King Abdullah University of Science and Technology.
Over the past decade, the frontier of biomaterials science has involved the use of MOMs, including the popular metal-organic frameworks (MOFs), to immobilize enzymes during biocatalysis. Biocatalysis is speeding up chemical reactions in biological systems with natural catalysts, such as enzymes, performing chemical transformations on organic compounds or biomacromolecules. At the conclusion of these chemical reactions, enzymes are typically unrecoverable as they remain mixed in solution with the products in which they have interacted. Yang and Chen’s novel solution allows for the enzymes to be isolated and extracted, allowing them to be used again and again saving energy, electricity, human labor effort, and funding for both researchers and industry.
While there are other methods currently used to immobilize and isolate enzymes, they are often limited by an individual enzyme’s dimension, surface charge, and substrate size. In addition, many immobilization platforms and materials are unstable under either acidic or basic pHs, so the catalytic reaction conditions are limited.
To create a platform that could be used for all enzymes regardless of these limitations, Yang and Chen developed what they call the Ca-MOM system, wherein Ca2+ and a few carboxylate compounds can form co-crystals while entrapping enzymes in water. Most importantly, the formed biocomposites are stable under an extremely wide range of pH. The chemicals needed to make Ca-MOM are cheap and the reaction is a completely green synthesis using water without any additional requirements of power, pressure, temperature, or even sunlight and Ca-MOM immobilizes enzymes under a very wide range of pH.
The team demonstrated the viability of Ca-MOM by isolating four key enzymes already used widely in research and industry: lysozyme (which degrades bacterial cell walls), lipase (which breaks down dietary fats into smaller molecules), and glucose oxidase and horseradish peroxidase (both degrade the reactive oxygen species which are a major threat to human health). The research showed that following biocatalysis, each enzyme’s function was not changed and they were all able to be reused. Reusing enzymes many times over and the near-zero cost of the synthetic conditions will significantly reduce the cost of any reactions requiring enzymes.
While it was exciting to develop the new materials, the team did not stop. The next step for the team is to understand how the enzymes work within their MOMs, or, the structural basis of the enzyme performance.
The team has complemented their initial research with site-directed spin labeling and electron paramagnetic resonance spectroscopy to probe the differences in enzyme performance on MOMs formed by Ca2+ and different ligands. SDSL-EPR is unique in its capability to probe structure and dynamics information at a high resolution regardless of any background interferences. Being able to determine the backbone dynamics of an enzyme at the residue level using SDSL-EPR, the team discovered that the enzyme can possess higher dynamics in one of the Ca-MOMs, which explains the relatively high catalytic efficiency in this specific MOM.
This method caused attention during the review of the first article and generated an invitation from the editorial office to introduce the methodology. Yang and Chen published one work in the research article section and the second in the resources section of the first issue of Chem Catalysis.
The new platform along with the comprehensive analysis tool will allow for more enzymes to be widely reused and stimulate the development of enzyme immobilization platform design benefiting both research and industry.
Funding was provided by the NDSU New Faculty Startup funds, NSF CAREER Award and USDA-NIFA.
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