Engineering enzymes to perform reactions not found in nature can address long-standing challenges in the world of synthetic chemistry, such as transforming vegetable oils into useful biochemicals.
A team of researchers has developed a simple yet powerful strategy to create new enzymes with new reactivity that can produce valuable chemical compounds, building on their previous work using light to reuse natural enzymes.
The study, published in Nature Catalysis, was led by Xiaoqiang Huang, a former postdoctoral researcher in the Department of Chemical and Biomolecular Engineering (ChBE) at the University of Illinois at Urbana-Champaign and the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI), a research center on bioenergy funded by the US Department of Energy. Huang, currently Assistant Professor at Nanjing University in China, carried out this work in the laboratory of Professor ChBE Huimin Zhao, CABBI’s Conversion Theme Leader and affiliate of the Carl R. Woese Institute for Genomic Biology (IGB) .
In the study, visible light was used to excite a modified ketoreductase enzyme, enabling a new-in-nature biocatalytic reaction known as asymmetric radical conjugate addition, which is extremely difficult to achieve by chemical catalysis.
Catalysts are substances used to speed up chemical reactions. In living organisms, protein molecules called enzymes catalyze reactions in a process called biocatalysis. Scientists have started using biocatalysis to synthesize valuable compounds because its high selectivity allows them to deploy enzymes to act on specific substrates and create target products. Another advantage is that the enzymatic reactions are highly durable. They are relatively inexpensive, consume little energy, and cause minimal environmental damage, unlike chemical catalysts, which typically require organic solvents, heat, and high pressure to operate.
However, enzymes are complicated to work with. They are normally limited to catalyzing reactions found in nature, which means scientists often struggle to find the perfect biocatalyst to meet their needs. Zhao’s lab focused on driving biocatalysis with visible light, a process known as “photobiocatalysis,” to produce novel enzyme reactivity. In a previous study, Zhao and Huang developed a visible light-induced reaction using an enzyme called ene-reductase (ER) as a biocatalyst to produce high yields of valuable chiral carbonyl compounds, which have potential applications for the production of high value chemicals.
The new study builds on this work, using photobiocatalysis on a different family of enzymes – the nicotamide-dependent ketoreductases produced by bacteria – and a different chemical mechanism to produce another type of chiral carbonyl compounds called α-esters. chiral. Through enlightenment and evolution of ketoreductase, the team achieved a Giese-like enantioselective biocatalytic radical conjugate addition to transform fatty acids into α-chiral esters, Zhao said.
Enantioselectivity is the degree to which an enantiomer – one of a pair of molecules that are mirror images of each other – is preferentially produced in a chemical reaction. Chirality is a fundamental characteristic of organic compounds, which greatly influences the properties of molecules, and its implications are enormous in many fields, including biology, medicine and materials science. For example, the diverse stereochemistry of organic molecules (the spatial arrangement of atoms and its effect on chemical reactions) not only greatly enhances the richness of the biological world, but also plays a profound role in many biological activities such as molecular communication , did he declare. .
The results offer practical applications for CABBI’s work to develop biofuels and biochemicals from crops such as miscanthus, sorghum and energy cane instead of petroleum. The new biocatalytic transformation could use the fatty acids that CABBI generates from these plants as raw materials to synthesize value-added bioproducts – such as ingredients for soaps or skin care products – in an environmentally friendly way. environment.
“Although we did not target a specific product for further application, this work provides a practical new method that could potentially be applied to fatty acid upgrading,” Zhao said. “Enzymes are the workhorses for the biological synthesis of fuels and chemicals from renewable biomass.
“One of the major scientific shifts in CABBI conversion research, or bioenergy research in general, is the lack of known enzymes with the desired activity and substrate specificity for the synthesis of fuels and target chemicals. Therefore, there is an urgent need to develop new strategies to discover or design enzymes with the desired activity or reactivity.”
Study co-authors included CABBI postdoctoral fellow Guangde Jiang of ChBE; CABBI’s Wesley Harrison, a ChBE and IGB Ph.D. candidate; Jianqiang Feng and Binju Wang from Xiamen University, China; and Jiawen Cui, Xin Zang and Jiahai Zhou from the Shanghai Institute of Organic Chemistry, China. Zhou is also affiliated with the Chinese Academy of Sciences at the Institute of Advanced Technology in Shenzhen, China.