| The publication capped a 12-year effort
and can offer some insights into how industrial
processes might be improved, explained Michael Chan,
professor of biochemistry, and Joseph Krzycki, professor
of microbiology, both of Ohio State University. “This
enzyme is the key to the whole process of methanogenesis
from acetic acid,” Krzycki said. “Without it, this form
of methanogenesis wouldn’t happen. Since it is so
environmentally important worldwide, the impact of
understanding this would be enormous.”
Methanogenesis is the process by which the gas
methane is made, and it takes place everywhere across
the globe, from swamps to landfills, releasing the gas
that ultimately seeps into the atmosphere.
One central player in this process is the microbe
called Methanosarcina barkeri, a member of an
unusual group of organisms called the Archaea
that is similar to both bacterial and animal cells.
This organism possesses large amounts of the enzyme so
important for making methane.
“We often think only of humans putting carbon dioxide
and methane into the atmosphere but natural biology
itself actually provides its own sizeable share,” said
Chan. “This enzyme plays an important role in the
process that converts acetate into these two gases.”
The research can be traced to work that Krzycki did
as a graduate student in the mid-1980s studying the
protein known as acetyl-CoA decarbonylase/synthase (ACDS).
He was focusing on whether carbon monoxide oxidation was
part of the process of methanogenesis from acetate,
which had not been suspected before.
In 1995, Chan approached Krzycki about working with
this protein as one of the first projects Chan took on
after coming to Ohio State. The goal was to use protein
crystallography to get a picture of it and figure out
how it works.
An important initial step in this kind of research is
to “grow” crystals of the protein molecules, and from
these crystals, scientists can actually map out the
protein’s structure. “We tried for six months when I
first arrived at Ohio State but at the end of that
period, we couldn’t get any crystals to grow,” Chan
said.
Two years later, Chan and a former graduate student,
Bing Hao, went back to look at those previous
crystallization experiments and discovered that
crystals had eventually grown.
“The identification of these crystals allowed us to
solve the structure of the protein making up the
crystals, although it took 10 more years to do that,”
he said. “From the structure, we got a beautiful
picture of the protein that we could use to understand
how it works. Viewing a structure is somewhat like
looking at the schematics of an engine.”
Krzycki said that processes similar to those
performed by this protein are currently being used in
industry, although in those cases, high temperatures
are required.
“From studying this process in these microbes,
hopefully scientists can understand how their natural
catalysts make this reaction work at lower
temperatures,” he said.
Along with Chan, Krzycki and Hao, Weimin Gong,
Zhiyi Wei, Donald Ferguson Jr. and Thomas Tallant also
worked on the project. The research was supported by
grants from both the National Institutes of Health and
the Department of Energy.
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Source:-
Ohio State University
Published on 18th
July 2008
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