Primary structure analysis and functional expression of erythrose reductases from erythritol-producing fungi (Trichosporonoides megachiliensis SNG-42)

NADPH-dependent erythrose reductases (ERs) in erythritol-producing fungi, Trichosporonoides megachiliensis SNG-42, catalyze the reduction Of D-erythrose. We previously characterized the biochemical properties of three isozymes of ERs (ER-I, ER-II, and ER-III). Using internal amino acid sequences of ER-III and ER-I with peptide mapping, we cloned three cDNAs (er1, 1121-bp (AB191474); er2, 1077-bp (AB191475); er3, 1119-bp (AB191476)). The er3 cDNA encoded a polypeptide 36,044 Da, and its deduced amino acid sequence was same as that of the native ER-III. The three recombinant enzymes expressed in Escherichia coli were purified to homogeneity. The recombinant enzymes of ER1, ER2, and ER3 showed similar electrophoretic properties to that of the native ER-I, ER-II, and ER-III on SDS- and Native- but not on IEF-PAGE. All three recombinant enzymes showed substrate specificity towards C-4 and C-3 aldehydes similar to that of the native ER-III. These results strongly suggest that cloned er1, er2, and er3 cDNAs encode erythrose reductases.