Iowa State researcher studies how enzymes break down cellulose
Peter Reilly pointed to the framed journal covers decorating his office. Each of the six showed the swirling, twisting, complicated structure of an enzyme. Those bright and colorful illustrations are the work of his lab. And they鈥檙e part of Reilly鈥檚 work to understand how the structure of an enzyme influences its mechanism and its activity.
In other words, he鈥檚 trying to figure out 鈥渉ow is it that these things work,鈥� said Reilly, a professor of chemical and biological engineering and an Anson Marston Distinguished Professor of Engineering at Iowa State University.
That鈥檚 important because enzymes do a lot for all of us.
Enzymes are proteins produced by living organisms that accelerate chemical reactions. They, for example, work inside the human digestive system to break starch or protein molecules into smaller pieces that can be absorbed by the intestines. Enzymes are also used to produce bread, they鈥檙e added to detergents to clean stains and they鈥檙e used to treat leather. And because enzymes break down cellulose into simple sugars that can be fermented into alcohol, they鈥檙e a big part of producing ethanol from cellulose.
Reilly is particularly interested in the enzymes that work on cellulose. He has a three-year, $306,000 grant from the U.S. Department of Agriculture to develop a basic understanding of how they work.
Those enzymes are known as cellulases. They鈥檙e commonly produced by fungi and bacteria. And they鈥檝e got a very hard job.
Cellulose is tough stuff. It鈥檚 in the cell walls of plants. It鈥檚 what gives a plant its structure.
鈥淚t鈥檚 why trees stand up,鈥� Reilly said.
He also said, 鈥淣ature has done its best to break down cellulose.鈥�
So different enzymes have developed different ways of attacking cellulose.
One enzyme Reilly has studied and illustrated 鈥� a cellobiohydrolase enzyme 鈥� has an extension that works like a little plow. It rips up one cellulose chain from a cellulose crystal and feeds it into a tunnel on the main enzyme surface so that it can be chopped up.
Reilly, who can鈥檛 resist a lesson in biochemistry, likes to explain how enzymes attack and break chemical bonds. He鈥檒l display diagrams on his office computer that show the bonds in cellulose molecules. He鈥檒l point out where enzymes attack some of those bonds. He鈥檒l say the chemical reactions create high-energy transition states that scientists are working hard to understand. And he鈥檒l get back to the bottom line.
鈥淭hese different enzymes all do the same thing,鈥� Reilly said. 鈥淭hey all break down bonds between the sugars that make up cellulose.鈥�
And, he said, 鈥淔or something that鈥檚 not alive, enzymes are awfully sophisticated.鈥�
Reilly鈥檚 students use a lot of computing power to figure out how enzymes are put together. They routinely work with CyBlue, Iowa State鈥檚 supercomputer capable of 5.7 trillion calculations per second, and Lightning, an Iowa State high-performance computer capable of 1.8 trillion calculations per second.
By adding to the basic understanding of enzymes, Reilly is opening doors for new and better applications of enzymes. Better enzymes, for example, could be the key to making the production of cellulosic ethanol more efficient and more economical.
There鈥檚 still a lot for chemical engineers to learn about the specialized proteins.
After all, Reilly said, 鈥淣ature has tried over and over to find ways to break down cellulose.鈥�
Source: Iowa State University
