Kappa-carrageenase, member of glycosyl hydrolase family 16
Kappa-carrageenase is a glycosyl hydrolase family 16 (GH16) member that hydrolyzes the internal beta-1,4-linkage of kappa-carrageenans, a hydrophilic polysaccharide found in the cell wall of Rhodophyceaea, marine red algae. Carrageenans are linear chains of galactose units linked by alternating D-alpha-1,3- and D-beta-1,4-linkages that are additionally modified by a 3,6-anhydro-bridge. Depending on the position and number of sulfate ester modifications they are subdivided into kappa-, iota-, and lambda-carrageenases, kappa being modified once. Carrageenans form thermo-reversible gels widely used for industrial applications. Kappa-carrageenases exist in bacteria belonging to at least three phylogenetically distant branches, including pseudoalteromonas, planctomycetes, and baceroidetes. This domain adopts a curved beta-sandwich conformation, with a tunnel-shaped active site cavity, referred to as a jellyroll fold.
Jiyao W et al.(2023). "The conserved domain database in 2023.",