Promotes cell surface expression of the potassium channel KCND2 (PubMed:22311982). Modulates the activity and gating characteristics of the potassium channel KCND2 (PubMed:22311982). Has no dipeptidyl aminopeptidase activity (Probable). May form oligomers. Interacts with KCND1 and KCND2 (By similarity). Detected in brain cortex (at protein level) (PubMed:22311982). Expressed in the brain, predominantly by neurons and not by glia. N-glycosylation is important for cell surface expression, specially at Asn-258, which is crucial. Belongs to the peptidase S9B family. DPPIV subfamily. Gly-652 is present instead of the conserved Ser which is expected to be an active site residue suggesting that this protein has no peptidase activity.