A team of researchers led by NDSU assistant professors Zhongyu Yang (chemistry and biochemistry) and Bingcan Chen (plant sciences) have recently published two articles focused on the development of metal-organic materials (MOMs) 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.
Over the past decade, the frontier of biomaterials science has involved the use of MOMs to immobilize enzymes during biocatalysis. Biocatalysis is the process of 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 with 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 thus 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. 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.
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, PhD, Qiaobin Li, and Mary Lenertz; and collaborators from Purdue University and King Abdullah University of Science and Technology.
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.
The next step for the team is to understand how the enzymes work within their MOMs, or, the structural basis of the enzyme performance. This is a tough task due to the difficulty in obtaining enzyme structure and dynamics information at sufficient resolution under the interference of the MOM materials.
The team complemented their initial research with site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy. This process probes the differences in enzyme performance on Ca2+ MOMs and different ligands (bonding molecules). 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 an enzyme can possess higher dynamics in one of the Ca-MOMs, which explains the higher catalytic efficiency of the new MOM.
Yang and Chen hope that 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.
Because of attention generated by the new method during the review of the first article, the Chem Catalysis editorial office invited the team to introduce the methodology in a second article. Yang and Chen then published one article in the research section and a second in the resources section of the first issue of Chem Catalysis.
Funding was provided by the NDSU New Faculty Startup funds, NSF CAREER Award (MCB), and USDA-NIFA. For more information, see: