The essentially irreversible reduction of furfural catalyzed by this enzyme supports its functional designation as an NADPH-linked furfural reductase. The only other bacterial enzyme activities that have been implicated in furfural metabolism are a furfuryl alcohol dehydrogenase and a furfural dehydrogenase from P. putida Fu1 (Koenig and Andreesen, 1990) that presumably contribute to an oxidative pathway not unexpected for such a versatile oxidative organism. These enzymes were shown to respectively catalyze the oxidation of furfuryl alcohol to furfural, and furfural to 2-furoic acid, with each reaction utilizing NAD+ as natural co-enzyme. An enzyme activity that participates in NADH-dependent reduction of furfural in yeast has been reported but not characterized (Wahlbom and Hahn-Hagerdal, 2002).