This superfamily consists of diapausin-related antimicrobial peptides. Diapause during periods of environmental adversity is an essential part of the life cycle of many organisms, with the molecular basis being different among animals. Diapause-specific peptides (DSP) provide anti-fungal activity and act as N-type voltage-gated calcium channel blocker []. The overall structure of DSP is compact due to the three disulfide bridges that indicate a high similarity with insect- and plant-derived antifungal peptides. The DSP structure includes two α-helices and a triple-stranded β-sheet. The three disulfide bridges (Cys-7/Cys-21, Cys-11/Cys-33, and Cys-22/Cys-40) help the link between helices and the β-sheets [].
Proteins containing this domain include vertebrate dual specificity protein phosphatase Laforin and plant starch excess4 (SEX4). Laforin (encoded by the EPM2A gene) is a dual-specificity phosphatase that dephosphorylates complex carbohydrates. Mutations in the EPM2A gene cause Lafora disease (LD), a fatal autosomal recessive neurodegenerative disorder characterised by the presence of progressive neurological deterioration, myoclonus, and epilepsy []. Pathologically, LD is characterised by distinctive polyglucosans, which are formations of abnormal glycogen []. Laforin prevents LD by at least two mechanisms: by preventing hyperphosphorylation of glycogen by dephosphorylating it, allowing proper glycogen formation, and by promoting the ubiquitination of proteins involved in glycogen metabolism via its interaction with malin. Laforin contains an N-terminal CBM20 (carbohydrate-binding module, family 20) domain and a C-terminal catalytic dual specificity phosphatase (DSP) domain [].Plant SEX4 (also known as DSP4) regulates starch metabolism by selectively dephosphorylating glucose moieties within starch glucan chains. It contains an N-terminal catalytic DSP domain and a C-terminal Early (E) set domain [].
