Members of this protein family include secreted (or membrane-anchored) pullulanases of Gram-negative bacteria and pullulanase-type starch debranching enzymes of plants. Both enzymes hydrolyze alpha-1,6 glycosidic linkages. Pullulan is an unusual, industrially important polysaccharide in which short alpha-1,4 chains (maltotriose) are connected in alpha-1,6 linkages. Enzymes that cleave alpha-1,6 linkages in pullulan and release maltotriose are called pullulanases although pullulan itself may not be the natural substrate. This family is closely homologous to, but architecturally different from, the Gram-positive pullulanases of Gram-positive bacteria (TIGR02102). [Energy metabolism, Biosynthesis and degradation of polysaccharides]
Jiyao W et al.(2023). "The conserved domain database in 2023.",