Purification and properties of a NADPH-dependent erythrose reductase from the newly isolated Torula corallina.

Torula corallina (KCCM-10171) is a yeast strain that is currently used for the industrial production of erythritol and has the highest erythritol yield ever reported for an erythritol-producing microorganism. Production of erythritol in T. corallina is catalyzed by erythrose reductase, an enzyme that converts erythrose to erythritol using NADPH as a cofactor. In this study, NADPH-dependent erythrose reductase was purified to homogeneity from the newly isolated T. corallina. The relative molecular weight of the erythrose reductase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size exclusion chromatography was 35.4 and 71.0 kDa, respectively, indicating that the enzyme is dimeric. This enzyme catalyzed both erythrose reduction and erythritol oxidation; both enzyme activities required NADP(H). The pH and temperature optima for erythrose reduction and erythritol oxidation were 6.0, 40 degreesC and 8.0, 45 degreesC, respectively. The sequence of the first 10 amino acids of this enzyme was N-V-K-N-F-Y-Q-P-N-D. The affinity (K-m = 7.12 mM) of the enzyme for erythrose was comparable to that of other known erythrose reductases, and the specificity for erythrose was very high, resulting in no production of other polyols, which may explain the high erythritol yield observed in this strain.