1.2.1.100	5-formyl-3-hydroxy-2-methylpyridine-4-carboxylate + NAD+ + H2O	-	
1.2.1.100	additional information	enzyme catalyzes oxidation of the hemiacetal form of 5-formyl-3-hydroxy-2-methylpyridine-4-carboxylate to 3-hydroxy-2-methylpyridine-4,5-dicarboxylate with NAD+ and reduction of an aldehyde form of 5-formyl-3-hydroxy-2-methylpyridine-4-carboxylate to 4-pyridoxic acid with NADH, i.e. reaction of 4-pyridoxic acid dehydrogenase. The Ser-His-Glu catalytic triad facilitates the two-way reactions. Ser116 assists protonation of His137 to drive the reduction reaction. His137 acts as a catalytic base to abstract a proton during oxidation. Glu149 likely neutralizes the positive charge on His137 after the deprotonation of the substrate