Pork liver has been shown to contain a soluble enzyme,L-fuconate hydro-lyase (L-fuconate dehydratase), capable of dehydratingL-fuconate to 2-keto-3-deoxy-L-fuconate. The enzyme has been partially purified. TheKmforL-fuconate is 1.0 mM;D-arabonate is also an excellent substrate (Km1.3 mM) but the enzyme is inactive withD-fuconate,L-arabonate,D-gluconate,D-gulonate,D-galactonate,L-mannonate, andD-glucuronate. The enzyme has a sharp pH optimum at pH 7.0, requires Mg2+for activity, and is inhibited byp-hydroxymercuribenzoate. The substrate specificity ofL-fuconate hydro-lyase resembles that of pork liverL-fucose: NAD oxidoreductase and it is suggested that these enzymes serve in the metabolism ofL-fucose by the following pathway:L-fucose → L-fucono-1,5-lactone → L-fuconate → 2-keto-3-deoxy-L-fuconate. The metabolic fate of the latter compound is not known.D-Arabinose can be metabolized by pork liver by an analogous pathway.