Researchers shed light on new enzymatic reaction

Date:
June 8, 2020
Source:
University of Illinois at Urbana-Champaign Institute for
Sustainability, Energy, and Environment
Summary:
Researchers have discovered that repurposed enzymes and light
are key to producing chemical compounds in an environmentally
friendly fashion. By blending bio- and photocatalysis and
experimenting with reactionary 'ingredients,' the research team
developed a visible-light-induced reaction using the enzyme family
ene-reductase (ER). The substrates used in this study, alkenes,
can be derived in principle from biomass fatty acids; the end
products are valuable chiral carbonyl compounds with potential
pharmaceutical applications.



FULL STORY ========================================================================== Researchers have identified key ingredients for producing high-value
chemical compounds in an environmentally friendly fashion: repurposed
enzymes, curiosity, and a little bit of light.


==========================================================================
A paper published in Nature describes a study led by Xiaoqiang Huang (pictured), a postdoctoral researcher in the University of Illinois at
Urbana- Champaign's Department of Chemical and Biomolecular Engineering
(ChBE) and the Carl R. Woese Institute for Genomic Biology (IGB). Huang
works in the lab of ChBE Professor Huimin Zhao, Conversion Theme Leader
at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI),
a U.S. Department of Energy- funded Bioenergy Research Center (BRC).

Catalysts are substances used to speed up chemical reactions; in living organisms, protein molecules called enzymes catalyze reactions in a
process called biocatalysis.

Biocatalysis is rapidly emerging as a nuanced, agile way to synthesize
valuable compounds. Scientists are investigating the ability of enzymes to catalyze diverse reactions, and for good reason: biocatalytic reactions
are highly selective, meaning that scientists can use enzymes to act on specific substrates and create target products.

Enzymatic reactions are also highly sustainable as they are relatively inexpensive, consume low levels of energy, and do minimal damage to the environment: while chemical catalysts typically require organic solvents,
heat, and high pressure to function, biocatalysts work in aqueous
solutions, operating at room-temperature and normal-pressure conditions.

Despite their value to science and sustainability, enzymes can be
complicated to work with. Reactions enzymes can catalyze are limited
to those found in nature; this means that scientists often struggle to
track down the perfect biocatalyst to meet their need.



==========================================================================
The process is similar to mixing paint: How can an artist creatively
combine the colors already on a palette to produce the right shade? In
the language of a chemical reaction: How can scientists leverage
enzymes already existing in nature to create the products they need?
The research team developed a solution: a visible-light-induced reaction
that uses the enzyme family ene-reductase (ER) as a biocatalyst and can
produce high yields of valuable chiral carbonyl compounds.

"Our solution might be considered 'repurposing.' We take known enzymes
that occur in nature, and repurpose them for a novel reaction," Zhao said.

In other words, the researchers didn't need to add a new kind of paint
to the palette -- they discovered an artful way to combine what was
already there.

These "repurposed" enzymatic reactions are not only economically and environmentally efficient, but highly desirable: chiral carbonyl compounds
have potential applications in the pharmaceutical industry to be used
for drug production.



==========================================================================
The team's solution is particularly unique in that it merges biocatalysis
with photocatalysis -- wherein light is used as a renewable source of activation energy -- in a novel, photoenzymatic reaction.

Over the course of the study, researchers tested a variety of substrates
(i.e., the substance on which the catalyst acts), documenting the ER
enzymes' reactivity in response to each. This process is comparable to
baking a chemical chocolate-chip cookie: by keeping light levels constant
and tweaking the "ingredients" (i.e. ERs and substrates), the team was
able to gradually circle in on a desired reaction.

Using chemical insights and clever design to synthesize value-added
products is characteristic of CABBI's Conversion theme.

"Creating novel enzyme function is one of CABBI's major scientific
challenges," Zhao said. "This study addresses that challenge by
uncovering novel uses for enzymes and showing what they're capable of."
The substrates used in this study (hydrocarbon compounds known as alkenes)
also align with CABBI's mission to investigate applications of plant
biomass. In principle, fatty acids from crops like miscanthus, sorghum,
and sugarcane can be converted into alkenes, which can then be used in
place of petroleum-based substrates to produce valuable compounds.

By blending bio- and photocatalysis and experimenting with various
reactionary "ingredients," this study expanded the ER enzyme's repertoire
to synthesize high-value, high-quantity compounds.

But merging light with enzymes is just the beginning.

"We are by no means limited to creating chiral carbonyl compounds,"
Huang said.

"Hopefully, this research will inspire scientists to combine several
types of enzymes and explore new options for reactivity." In the
future, researchers can build on this study to create an even more
diverse portfolio of products -- and further expand upon the economic
and environmental benefits of enzymes.


========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign_Institute_for Sustainability,_Energy,_and_Environment. Original written by Jenna
Kurtzweil.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Xiaoqiang Huang, Binju Wang, Yajie Wang, Guangde Jiang, Jianqiang
Feng,
Huimin Zhao. Photoenzymatic enantioselective intermolecular radical
hydroalkylation. Nature, 2020; DOI: 10.1038/s41586-020-2406-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200608134408.htm

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