Isolation of diphosphopyridine nucleotide-dependent L-fucose dehydrogenase from pork liver.

A DPN+-dependent L-fucose dehydrogenase has been isolated from pork liver and purified over 300-fold by a combination of ammonium sulfate fractionation, diethylaminoethyl cellulose chromatography, gel filtration on Sephadex G-100, and preparative polyacrylamide gel electrophoresis. The pH optimum for the dehydrogenase was 8.7 and K,,, values were 2.0 x 10d5 M for DPN+ and 3.2 x 10m4 M for L-fucose. The immediate product of L-fucose oxidation was shown to be L-fuconolactone (probably the l--f 5 isomer); the lactone was hydrolyzed spontaneously to Lfuconate at the pH of the reaction. The purified enzyme also catalyzed the oxidation of L-galactose (Km 8.0 x lOMa M), n-arabinose (Km, 2.1 X 1O-a M), and 3-amino-3-deoxy-Darabinose (Km, 8.0 x 10ea M); all active sugars have the same hydroxyl group configurations from C-2 to C-4. The 2-, 3-, or 4-epimers of D-arabinose were much less effective substrates for the enzyme (K, > 3 X 10m2 M). ATP -+ L-fuculose-1-P + ADP; n-fuculose-1-P + L-lactaldehyde + dihydroxyacetone-P. In animals, the following experiments in vivo have been reported. (A) Following the administration of n-fucose-1-14C to humans (15), 40% of the labeled carbon was expired as CO2 within 6 hours. (5) In a similar experiment in the rat, less than 2’% of the administered n-fucose-lJ4C was converted to 14C02 in 6 hours, while 30% appeared as unchanged fucose in the urine (10, 11). These results suggest substantial differences between species in their ability to catabolize Lfucose. The present report concerns the isolation of an n-fucose dehydrogenase from pork liver that catalyzes the following reaction.