Disproportionating enzyme 2 (DPE2), N-terminal CBM20 (carbohydrate-binding module, family 20) domain, repeat 1. DPE2 is a transglucosidase that is essential for the cytosolic metabolism of maltose in plant leaves at night. Maltose is an intermediate on the pathway from starch to sucrose and DPE2 is thought to metabolize the maltose that is exported from the chloroplast. DPE2 has two N-terminal CBM20 starch binding domains as well as a C-terminal amylomaltase (4-alpha-glucanotransferase) catalytic domain. DPE1, the plastid version of this enzyme, has a transglucosidase domain that is similar to that of DPE2 but lacks the N-terminal carbohydrate-binding domains. The CBM20 domain is found in a large number of starch degrading enzymes including alpha-amylase, beta-amylase, glucoamylase, and CGTase (cyclodextrin glucanotransferase). CBM20 is also present in proteins that have a regulatory role in starch metabolism in plants (e.g. alpha-amylase) or glycogen metabolism in mammals (e.g. laforin). CBM20 folds as an antiparallel beta-barrel structure with two starch binding sites. These two sites are thought to differ functionally with site 1 acting as the initial starch recognition site and site 2 involved in the specific recognition of appropriate regions of starch.
Jiyao W et al.(2023). "The conserved domain database in 2023.",