New Molecule May Aid In Production Of Biofuels And Fungi-resistant Plants

The research appears as the "Paper of the Week" in the August 5issue of the Journal of Biological Chemistry, an American Society forBiochemistry and Molecular Biology journal.

"Chitin is an insoluble molecule that consists of tightlypacked chains of polymerized sugars," explains study author Dr. VincentG. H. Eijsink of the Norwegian University of Life Sciences. "It issynthesized by different crustaceans, mollusks, algae, insects, fungiand yeasts and is a major structural component of these organisms. Forexample, chitin gives strength and stiffness to the shells/cuticles ofshrimps and insects and to the cell walls of fungi. Because chitin isan abundant resource and, most importantly, because it occurs inseveral types of plague organisms and parasites, chitin degradation isof great interest to humanity. For example, insects might be combatedby interfering with their chitin metabolism. Insect viruses need todegrade insect chitin for infection. Fungi may also be combated bydegrading the chitin in their cell walls."

More than one billion tons of chitin are produced by insects,fungi, and marine organisms every year. Despite this abundantproduction, chitin does not accumulate in most ecosystems, indicatingthat the molecule is somehow degraded. Many aquatic and terrestrialmicroorganisms produce enzymes called chitinases which are responsiblefor breaking down chitin. Because chitin is a very tough molecule,chitinases have quite a challenge. In order to break the bonds betweenthe sugar units, they must gain access to the bonds by somehowdisrupting the packing of the sugar chains in the chitin molecule. Howexactly chitinases overcome these challenges has been unclear untilnow.

Interested in learning more about how the breakdown of chitinoccurs, Dr. Eijsink and his colleagues investigated chitin degradationby the soil bacterium Serratia marcescens. They discovered that inaddition to producing chitinases, the bacterium also make a proteincalled CBP21 which binds to and disrupts the chitin polymer making itmore accessible to degradation by chitinases. They showed that addingCBP21 dramatically speeds up the degradation of chitin by chitinases.CBP21 works by binding to chitin through highly specific interactionsthat disrupt the chitin structure making the individual sugar chains inthe chitin polymer more amenable to enzymatic degradation.

The discovery of this new protein that participates in chitindegradation has many potential applications. For example, transgenicplants that expresses both chitinases and CBP21 would be able to combatfungi by degrading chitin in their cell walls. And, a betterunderstanding of natural chitin turnover increases our ability tointerfere with chitin metabolism in insects and other plague organisms.

CBP21 also has the potential to aid in the production ofbiofuel. "In principle, large quantities of chitin are available forexploration, primarily due to fishing and farming of crustaceans suchas shrimps," says Dr. Eijsink. "However, a current lack of technologylimits the exploitation of these waste streams. CBP21-like proteins maybecome an important tool for effective, enzymatic processing of thisvaluable resource. More in general, one might say that our discoverymay lead to discovery of proteins with similar functions in celluloseprocessing. This may be of major important for the cellulose field andproduction of biofuel."

The Journal of Biological Chemistry's Papers of the Week is anonline feature which highlights the top one percent of papers receivedby the journal. Brief summaries of the papers and explanations of whythey were selected for this honor can be accessed directly from thehome page of the Journal of Biological Chemistry online at www.jbc.org.

The American Society for Biochemistry and Molecular Biology(ASBMB) is a nonprofit scientific and educational organization withover 11,000 members in the United States and internationally. Mostmembers teach and conduct research at colleges and universities. Othersconduct research in various government laboratories, nonprofit researchinstitutions, and industry.

Founded in 1906, the Society is based in Bethesda, Maryland, onthe campus of the Federation of American Societies for ExperimentalBiology. The Society's primary purpose is to advance the sciences ofbiochemistry and molecular biology through its publications, theJournal of Biological Chemistry, The Journal of Lipid Research,Molecular and Cellular Proteomics, and Biochemistry and MolecularBiology Education, and the holding of scientific meetings.

For more information about ASBMB, see the Society's website at www.asbmb.org.

The manuscript for the paper can be downloaded from the following URL:http://www.jbc.org/cgi/content/short/280/31/28492