Involved in the degradation of pyridoxine or pyridoxamine (free, phosphate-unbound, forms of vitamin B6). Oxidizes pyridoxal to 4-pyridoxolactone, but does not have activity toward pyridoxal 5'-phosphate, pyridoxine, pyridoxamine, pyridoxamine 5'-phosphate, 4-phthalaldehyde, 2-nitrobenzaldehyde, pyridine, formaldehyde, 2-carboxybenzaldehyde or sugars. NAD(+) + pyridoxal = 4-pyridoxolactone + H(+) + NADH Optimum pH is 9.2. Retains 66% of maximum activity at pH 8.6 and 57% of maximum activity at pH 10.0. Optimum temperature is 50 degrees Celsius. 37% and 33% of maximum activity is seen at 30 and 55 degrees Celsius respectively. Stable for 10 minutes at 45 degrees Celsius or lower, 76% of activity remains following 10 minutes incubation at 50 degrees Celsius and 1.3% of activity remains following 10 minutes incubation at 60 degrees Celsius. Cofactor degradation; B6 vitamer degradation; 4-pyridoxate from pyridoxal: step 1/2. Homotetramer. Belongs to the short-chain dehydrogenases/reductases (SDR) family.