JBC, Vol. 250, Issue 16, 6185-6190, Aug, 1975
L-fucose metabolism in mammals. Purification of pork liver 2-keto-3-deoxy-L-fuconate:NAD+ oxidoreductase by NAD+-Agarose affinity chromatography
N. A. Nwokoro and H. Schachter
Pork liver has previously been reported to contain a soluble enzymatic
pathway which converts L-fucose to 2-keto-3-deoxy-L-fuconate and
D-arabinose to 2-keto-3-deoxy-D-arabonate. We now report the isolation from
pork liver of a soluble NAD+-dependent dehydrogenase which acts on both
2-keto-3-deoxy-L-fuconate and 2-keto-3-deoxy-D-arabonate. This enzyme has
been purified to homogeneity by a five-step procedure; the final step
involved affinity chromatography on NAD+-agarose. A purification factor of
about 3000-fold was achieved with a yield of over 20%. The enzyme was
homogeneous on polyacrylamide gel electrophoresis at pH 9.1 and 7.0 and on
the basis of sedimentation equilibrium analysis with the ultracentrifuge.
The molecular weight of the native enzyme is about 100,000 while disc gel
electrophoresis in the presence of sodium dodecyl sulfate and thiol showed
the presence of a polypeptide of molecular weight 26,800; these results
suggest that the enzyme is a tetramer. The enzyme has an isoelectric point
of 5.4. The enzyme is unstable in the dilute state and in the absence of
thiol but can be kept for 2 years at -70 degrees at a protein concentration
of 4 mg per ml and in the presence of 1 mM dithiothreitol.