Researchers from Purdue University have discovered the structure of the enzyme that makes cellulose. They believe this finding could lead to easier ways of breaking down plant materials to make biofuels and other products and materials. In addition the researchers say the findings provide a more detailed glimpse of the complicated process by which cellulose is produced. Cellulose is the foundation of the plant cell wall and can be converted to bioproducts such as biofuels and biochemicals. The research findings were published in The Plant Cell.
“Despite the abundance of cellulose, the nitty-gritty of how it is made is still a mystery,” said Nicholas Carpita, professor of plant biology. “Now we’re getting down to the molecular structure of the individual enzyme proteins that synthesize cellulose.”
Carpita explains that cellulose is composed of several dozen strands of glucose sugars linked together in a cablelike structure and condensed into a crystal. The rigidity of cellulose allows plants to stand upright and lends wood its strength. “Pound for pound, cellulose is stronger than steel,” said Carpita.
A large protein complex synthesizes cellulose at the surface of the plant cell. The basic unit of this complex is an enzyme known as cellulose synthase. The protein complex contains up to 36 of these enzymes, each of which has a region known as the catalytic domain, the site where single sugars are added to an ever-lengthening strand of glucose that will be fixed in the plant cell wall as one of the strands in the cellulose “cable.”
Carpita and a team of researchers used X-ray scattering to show that cellulose synthase is an elongated molecule with two regions – the catalytic domain and a smaller region that couples with another cellulose synthase enzyme to form a dimer, two molecules that are stuck together. These dimers are the fundamental building blocks of the much larger protein complex that produces cellulose.
“Determining the shape of cellulose synthase and how it fits together into the protein complex represents a significant advance in understanding how these plant enzymes work,” Carpita said. Continue reading