ABSTRACT
This chapter considers a group of important polysaccharides which in vivo are involved with the structure of land-based plants or parts of plants: fruits, general cell walls. Pectins occur as a major component in the cell walls of terrestrial plants, while the algal polysaccharides like carrageenans or alginates seem to serve a similar function in the cell walls of marine algae. There are a number of enzymes known to act on pectins. Amongst these, pectate lyase cleaves bonds between methylgalacturonate residues. Pectate lyases carry out a similar reaction between residues that lack the methyl group, to yield an unsaturated uronide. Enzymatic hydrolysis removes methyl groups from one end of the chain progressively and completely and can be controlled. Large-scale manufacture of apple juice has employed added pectin and polygalacturonase, the enzymes being obtained from fungi. Control of the degradation of pectins is one of the major commercial applications of polysaccharide biotechnology so far.
