Promotes cell surface expression of the potassium channel KCND2 (PubMed:15454437). Modulates the activity and gating characteristics of the potassium channel KCND2 (PubMed:15454437). Has no dipeptidyl aminopeptidase activity (PubMed:12662155). May form oligomers. Interacts with KCND1 (Probable). Interacts with KCND2. Additional isoforms seem to exist, which may have different subcellular locations. Found in serum, T-cells and brain (at protein level). Expressed in brain, pancreas, spinal cord and adrenal glands. N-glycosylation is important for cell surface expression, specially at Asn-257, which is crucial. Disease susceptibility is associated with variants affecting the gene represented in this entry. Belongs to the peptidase S9B family. DPPIV subfamily. Gly-651 is present instead of the conserved Ser which is expected to be an active site residue suggesting that this protein has no peptidase activity. Extended N-terminus.