POLYSACCHARIDE LYASES FROM GELLAN-PRODUCING SPHINGOMONAS SPP

A number of Sphingomonas strains capable of synthesizing the bacterial exopolysaccharide gellan and related polymers were shown to possess c onstitutive gellanase activity. In each case, the degradation of deacy lated gellan was due to extracellular, eliminase-type enzymes (lyases) which cleave the sequence ...beta-D-glucosyl 1,4-beta-D-glucuronosyl. .. in the tetrasaccharide repeat unit of the substrate polysaccharides . Deacetylated rhamsan was an alternative substrate but there was litt le or no action against most other polysaccharides with similar struct ures. Slight differences were found between the specificities of the l yases from different strains. Activities of gellan lyase preparations were generally low. As well as the extracellular 'gellanase' activity, all the bacteria possessed varying amounts of beta-D-glucosidase and beta-D-glucuronidase activities apparently located in the periplasm. T he products from deacylated gellan and the chemically deacylated form of polysaccharide S194 (rhamsan gum), which is effectively a gentiobio sylated form of gellan, closely resembled those recently obtained by t he authors from other, gellan-degrading, non-gellan-producing bacteria . The enzymes had negligible activity against the natural, acylated ge llan and rhamsan polysaccharides from bacteria now designated as strai ns of Sphingomonas.