ISOLATION AND CHARACTERIZATION OF L-FUCOSE DEHYDROGENASE FROM RABBIT LIVER

L-Fucose dehydrogenase [EC 1.1.1.122] was isolated from a rabbit liver extract and purified about 390-fold with a yield of approximately 13 %. The purification procedures included treatment with protamine, ammonium sulfate fractionation, treatment with acid, DE-32 cellulose column chromatography, gel filtration on Sephadex G-100, preparative polyacryl-amide gel electrophoresis, and affinity chromatography on 5' AMP-Sepharose 4B. The last procedure, affinity chromatography on 5' AMP-Sepharose 4B, was useful for the removal of other dehydrogenases.The enzyme which was homogeneous, as shown by polyacrylamide gel electrophoresis, had a molecular weight of about 92,000. The optimum pH was at 10.0 and isoelectric point at 5.2. The enzyme accepted both L-fucose and D-arabinose as substrate, but was specific for NAD+ as coenzyme. Km values were 0.15 mM, 1.4 mM, and 0.07 mM for L-fucose, D-arabinose, and NAD+, respectively.A single enzyme catalyzed the oxidation of L-fucose and D-arabinose, which had the same configurations of hydroxyl groups from C-2 to C-4. The reaction products obtained with L-fucose as substrate were L-fucono-lactone and L-fuconic acid. The L-fucono-lactone was an immediate product of oxidation and was hydrolyzed to L-fuconic acid spontaneously. This reaction- was irreversible. Therefore, it is likely that L-fucose dehydrogenase is involved in the initial step of the catabolic pathway of L-fucose in rabbit liver. © 1979, by the Japanese Biochemical Society.