Glycosaminoglycan (GAG) polysaccharide lyase family. This family consists of a group of secreted bacterial lyase enzymes capable of acting on glycosaminoglycans, such as hyaluronan and chondroitin, in the extracellular matrix of host tissues, contributing to the invasive capacity of the pathogen. These are broad-specificity glycosaminoglycan lyases which recognize uronyl residues in polysaccharides and cleave their glycosidic bonds via a beta-elimination reaction to form a double bond between C-4 and C-5 of the non-reducing terminal uronyl residues of released products. Substrates include chondroitin, chondroitin 4-sulfate, chondroitin 6-sulfate, and hyaluronic acid. Family members include chondroitin AC lyase, chondroitin abc lyase, xanthan lyase, and hyalurate lyase.
Lyase, catalytic. Members of this family are predominantly found in chondroitin ABC lyase I, and adopt a helical structure, with fifteen alpha-helices which are at least two turns long and several short helical turns. The bulk of the domain is formed by ten alpha-helices forming five hairpin-like pairs and arranged into an incomplete toroid, the (alpha/alpha)5 fold. Additionally, two long and two short alpha-helices at the N-terminus of the domain wrap around the toroid. At the C-terminal end of the toroid there is one additional short alpha-helix. This domain is required for degradation of polysaccharides containing 1,4-beta-D-hexosaminyl and 1,3-beta-D-glucoronosyl or 1,3-alpha-L-iduronosyl linkages to disaccharides containing 4-deoxy-beta-D-gluc-4-enuronosyl groups.
Lyase, N terminal. Members of this family are predominantly found in chondroitin ABC lyase I, and adopt a jelly-roll fold topology consisting of a two-layered bent beta-sheet sandwich with one short alpha-helix. The convex beta sheet is composed of five antiparallel strands, whilst the concave beta-sheet contains five antiparallel beta-strands with a loop between two consecutive strands folding back onto the concave surface. This domain is required for binding of the protein to long glycosaminoglycan chains.