Catalyzes the NAD(P)H-dependent reduction of pyridoxal to pyridoxine in vitro. Is not able to reduce 4-pyridoxate, and to oxidize pyridoxine or pyridoxamine. Has Kemp eliminase activity towards the non-physiological substrate 5-nitrobenzisoxazole, producing 4-nitro-2-cyanophenol; this activity is not considered to be physiologically relevant