Abstract
The synthesis, modification, and breakdown of carbohydrates is one of the most fundarnentally important reactions in nature. The structural and functional diversity of glycosides is mirrored by a vast array of enzymes involved in their synthesis (glycosyltransferases), modification (carbohydrate esterases ) and breakdown (glycoside hydrolases and polysaccharide lyases). The importance of these processes is reflected in the dedication of 1–2% of an organism’s genes to glycoside hydrolases and glycosyltransferases alone. In plants, these processes are of particular importance for cell-wall synthesis and expansion, starch metabolism, defence against pathogens, symbiosis and signalling. Here we present an analysis of over 730 open reading frarnes representing the two main c1asses of carbohydrate-active enzymes, glycoside hydrolases and glycosyltransferases, in the genome of Arabidopsis thaliana. The vast importance of these enzymes in cell-wall formation and degradation is revealed along with the unexpected dominance of pectin degradation in Arabidopsis, with at least 170 open-reading frarnes dedicated solely to this task.