Abstract
n-Hexanal (a major component of beany flavor) can be reduced to n-hexanol by endogenous alcohol dehydrogenase in a soybean extract. The substrate specificity for other aldehydes and the participation of coenzymes (NADH and NAD+) in this reaction were investigated. A soybean extract was incubated with various aliphatic aldehydes (carbon number 3-9) at 37°C, and the amount of alcohols formed was determined. The enzyme had a wide substrate specificity, the enzyme activity decreasing as the carbon number of the aldehydes increased (carbon number 3>4>5>6>7>9>8). The enzyme activity was markedly promoted by the addition of NAD+ as well as NADH. When a soybean extract was incubated with NAD+, NADH was formed, but no NADH was formed in the soybean extract after heating at 100°C for 5 min. These results suggest that NAD+ was converted to NADH by the action of an enzyme (s) in the soybean extract.
