Characterization of fatty alcohol:NAD+ oxidoreductase from rat liver.

Long chain fatty alcohols are known to be rapidly oxidized to the corresponding fatty acids in normal mammalian tissues in vivo. However, the enzyme system responsible for the reaction has not been well documented. We have demonstrated the conversion of (1-/sup 14/C)hexadecanol to (1-/sup 14/C)hexadecanoic acid using a cell-free system from rat liver. The subcellular distribution of this enzyme system parallels that of microsomal marker enzymes. The enzyme showed an absolute requirement for NAD/sup +/ and had a pH optimum of 8.4. Neither NADP/sup +/, NADH, nor NADPH can substitute for NAD/sup +/ as a cofactor. The reaction does not require oxygen. Albumin increases the rate of the reaction. The enzymic activity is not affected by including pyrazole, sodium azide, or AMP, ATP, and quinacrine in the incubation mixture. The apparent K/sub m/ for hexadecanol is 0.67 ..mu..M and the V/sub max/ is 5.98 nmol/min/mg of protein. The reaction product was identified as the fatty acid by both thin-layer and gas-liquid chromatography. Fatty aldehyde was also isolated and identified from the reaction mixture. Addition of semicarbazide to the incubation system increased the amount of fatty aldehyde produced with concomitant decrease in the formation of fatty acid. This documents that aldehyde more » is an intermediate in the reaction. This oxidoreductase is found in most tissues but has the highest activity in liver. « less