Best known for its ability to transform simmering pots of sugared fruit into marmalades and jams, pectin is a major constituent of plant cell walls and the middle lamella, the sticky layer that glues neighboring plant cells together. Pectin imparts strength and elasticity to the plant and forms a protective barrier against the environment. Several different kinds of pectic compounds combine to form pectin. The relative proportion of each of these depends on the plant species, location within the plant, and environment. Pectic compounds decorated with β-1,4-galactan (a chain of six-carbon sugars) are of considerable interest to the biofuels industry, because six-carbon sugars are readily converted into ethanol (biofuel) by fermenting microorganisms. A new study published in The Plant Cell reveals a novel enzyme involved in the production of β-1,4-galactans. This enzyme may be used to engineer plants with more desirable attributes for conversion to biofuel.
The major enzymes that catalyze pectin production are hard to pin down. Close to 70 enzymes are predicted to underlie pectin synthesis in plants; only about three of these have been identified definitively. Knowledge of these enzymes could be used to boost the production of pectins with desirable characteristics.
A team of researchers at the Joint BioEnergy Institute, University of California, Berkeley, and Technical University of Denmark set out to identify the enzymes that catalyze the production of β-1,4-galactan. They screened a database of enzymes for galactosyltransferases, the enzymes that link six-carbon galactose sugars into a chain. They found a family of proteins, named GT92, that are present in some animals and all plants sequenced to date. The authors found that mutations in each of the three genes encoding the GT92 proteins in the model plant Arabidopsis led to a reduction in β-1,4-galactan, whereas producing more of one of these proteins led to a
|Contact: Kathy R. Munkvold|
American Society of Plant Biologists