Regulatory subunit of the voltage-gated potassium (Kv) Shaker channels composed of pore-forming and potassium-conducting alpha subunits and of regulatory beta subunits (PubMed:11825900, PubMed:7649300). The beta-2/KCNAB2 cytoplasmic subunit promotes potassium channel closure via a mechanism that does not involve physical obstruction of the channel pore (PubMed:11825900, PubMed:7649300). Promotes the inactivation of Kv1.4/KCNA4 and Kv1.5/KCNA5 alpha subunit-containing channels (PubMed:11825900, PubMed:7649300). Displays nicotinamide adenine dinucleotide phosphate (NADPH)-dependent aldoketoreductase activity by catalyzing the NADPH- dependent reduction of a wide range of aldehyde and ketone substrates (By similarity). Substrate specificity includes methylglyoxal, 9,10- phenanthrenequinone, prostaglandin J2, 4-nitrobenzaldehyde, 4- nitroacetophenone and 4-oxo-trans-2-nonenal (in vitro, no physiological substrate identified yet) (By similarity). The binding of oxidized and reduced nucleotide alters Kv channel gating and may contribute to dynamic fine tuning of cell excitability (By similarity). Contributes to the regulation of nerve signaling, and prevents neuronal hyperexcitability (By similarity). {ECO:0000250|UniProtKB:P62482, ECO:0000250|UniProtKB:P62483, ECO:0000269|PubMed:11825900, ECO:0000269|PubMed:7649300}. This is the function of Ensembl gene identifier ENSG00000069424 (KCNAB2, potassium voltage-gated channel subfamily A regulatory beta subunit 2).