Most of the phosphorylases so far identified act on D-glucosides. This class of carbohydrates makes up the major energy storage and structural polysaccharides used in Nature but there are numerous other major naturally occurring polysaccharides: fructans are storage
polymers of fructose found in some plants and algae;133 plant cell walls contain many complex polymers, including xylans and uronic acid polymers;134 animals cells are covered in layers of charged polysaccharides, such as chondroitin and heparin;135 many types of seaweed have complex and charged polymers in their cell wall.136 With the large amounts of these compounds produced globally, it is likely there are many phosphorylases yet to be
identified that act on these materials. In order to find them, microbes that can use these alternative polysaccharides as carbon sources could be screened. Since many of these compounds are useful in biotechnology, food and medicine the possibility of synthesising
defined components, as offered by phosphorylases, is highly attractive.