\u3cem\u3eN\u3c/em\u3e-Acylethanolamines as Novel Alcohol Dehydrogenase 3 Substrates

N-Acylethanolamines (NAEs) are a class of fatty acid amides that act as important mammalian signaling molecules. N-Arachidonoylethanolamine is the best-studied representative and is one of the endogenous ligands for endocannabinoid receptors. NAEs play a role in the regulation of appetite, act as anti-inflammatory and analgesic agents, and are thought to have a neuroprotective function as well. They have been proposed to also serve as precursors to N-acylglycines (NAGs). N-Acylglycinals are likely to be intermediates between the NAEs and the NAGs. The sequential actions of a putative fatty alcohol dehydrogenase and a putative fatty aldehyde dehydrogenase are thought to affect the NAD+-dependent oxidation of the NAEs to the NAGs. NAGs, in turn, serve as precursor in the biosynthesis of primary fatty acid amides (PFAMs), another class of mammalian regulatory molecules. Alcohol dehydrogenase 3 (ADH3), an enzyme known to oxidize mid- and long-chain alcohols to aldehydes, was evaluated for its potential in oxidation of NAEs to N-acylglycinals. In order to evaluate the possibility of ADH3 involvement in NAE metabolism, variable chain length NAEs were synthesized and evaluated as substrates for bovine liver ADH3. NAEs were oxidized by ADH3 in the presence of NAD+, yielding the corresponding N-acylglycinals. VMax/KM values for assayed NAEs were low relative to cinnamyl alcohol, one of the preferred substrates for ADH3. Our data suggest that the ADH-mediated oxidation of NAEs could occur in vivo, but that ADH3 is unlikely to be the in vivo catalyst