Purification and Some Properties of an Erythrose Reductase from an Aureobasidium sp. Mutant.

An erythrose reductase was obtained from the cells of an Aureobasidium sp. mutant having high erythritol-producing activity. This enzyme was purified 600-fold over the cell-free extract by ammonium sulfate precipitation, ion exchange chromatography, affinity chromatography, and hydrophobic chromatography. It gave a single band on polyacrylamide gel electrophoresis, and had a molecular weight of 37,000 and an isoelectric point of 4.8. This enzyme had maximum reductive activity at 45°C and pH 6.5. The optimum pH of the oxidative reaction was 9.5. It was stable at pH 6.0-8.0 and below 40°C. The enzyme showed the maximum activity to D-erythrose. D-Glyceraldehyde was reduced at a rate 66% of that for D-erythrose. p-Nitrobenzaldehyde, L-erythrulose, dihydroxyacetone, and D-glucuronate were also reduced, although at slower rates. The oxidative activity was less than 0.1% of the reductive one.