2,6-Dihydroxypyridine is an alkaloid with the molecular formula C<sub>5</sub>H<sub>3</sub>N(OH)<sub>2</sub>. It is a colorless solid. 2,6-Dihyroxypyridine is an intermediate in the degradation of nicotine.
2,6-Dihydroxypyridine is an intermediate in the degradation of nicotine by the aerobic bacterium Arthrobacter nicotinovorans. The following reaction shows the formation of the intermediate from L-nicotine of tobacco.
The figure represents the pathway for the degradation of L-nicotine by A. nicotinovorans to 2,6-dihydroxypyridine
Another reaction of 2,6-dihydroxypyridine highlights its function as a substrate for oxygenase. One example is the enzyme monooxygenase, which oxidizes the substrate by transferring one oxygen atom of O<small>2</small> to the substrate. The other oxygen atom is reduced to water. The product of the oxidase reaction was determined to be 2,3,6-tri-hydroxypyridine because of the results of the stoichiometry as well as the results of the ultraviolet spectrum. This reaction can be shown by the following equation:
Arthrobacter oxydans, when grown on agar plates, were most active in the oxidation of 2,6-dihydroxypyridine.
2,6-Dihydroxypyridine in principle can exist in five tautomers:
The distribution of these tautomers is solvent-dependent. Studies show that tautomer II is most common in ethanol, water, and DMSO.
2,6-Dihydroxypyridine has been investigated in an oxidation method of dyeing hair. The process utilizes 2,6-dihydroxypyridine as a coupling agent, and 2,4,5,6-tetraaminopyrimidine as a primary intermediate. This oxidation method intensifies the color of the dyed hair for several days.
2,6-dihydroxypyridine is a key intermediate in the degradation of nicotine by certain bacteria. The enzyme 2,6-dihydroxypyridine-3-hydroxylase, which is produced in Escherichia coli, is responsible for catalyzing the sixth step of nicotine degradation in the bacterium Arthrobacter nicotinovoran. 2,6-dihydroxypyridine is hydroxylated by hydroperoxy-FAD. This reaction yields 2,3,6-tri-hydroxypyridine. This is shown in the following reaction:
2,6-dihydroxypyridine hydroxylase is a dimeric flavoprotein, with one bound FAD molecule attached. The reaction is NADH-dependent and the enzyme only accepts 2,6-dihydroxypyridine as a substrate. Furthermore, the enzyme is inhibited by 2,6-dimethoxypyridine and 2,3-dihydroxypyridine.