Promotes cell surface expression of the potassium channel KCND2. Modulates the activity and gating characteristics of the potassium channel KCND2 (PubMed:16123112, PubMed:19901547). Has no dipeptidyl aminopeptidase activity (Probable). May form oligomers. Interacts with KCND1 (By similarity). Interacts with KCND2 (PubMed:15671030, PubMed:16123112). Identified in a complex with KCND2 and KCNIP3 (PubMed:16123112). Detected in brain cortex, hippocampus, thalamus and cerebellum Purkinje cells (at protein level) (PubMed:16123112). N-glycosylation is important for cell surface expression, specially at Asn-257, which is crucial. 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.