Polysaccharides play many roles in organisms, and because they are biocompatible and biodegradable, these molecules are promising carrier materials for a broad range of therapeutics. The identity of individual sugar molecules in the chain, and the way they are linked together, make them function in different ways. Enzymes known as glycoside phosphorylases can cut certain polysaccharides apart or make new ones, depending on the reaction conditions. For example, one such enzyme makes chitin, the major component of arthropod exoskeletons and fungal cell walls. Stephen Withers and colleagues wondered if there might be previously unknown, naturally occurring enzymes that could make new types of polysaccharides.
Using genomic data and activity-based screening, the researchers identified a glycoside phosphorylase enzyme from bacteria called Acholeplasma laidlawii, a common contaminant of laboratory cell cultures. The team expressed and purified the enzyme, discovering that it could synthesize a new type of polysaccharide, which they named acholetin. The new biopolymer is similar in composition to chitin and to a biofilm-forming polysaccharide, but its sugar molecules are linked together in way that differs from these known biopolymers.
The team determined the crystal structure of the glycoside phosphorylase, which they suspect could be involved in maintenance of A. laidlawii's cellular membrane. As such, researchers might be able to target the enzyme to prevent cell culture contamination with the bacteria, in addition to using the enzyme to make the new biopolymer. Acholetin has wide-ranging potential as a new type of biocompatible, biodegradable material, the researchers say.