On a non‐pyridine nucleotide‐dependent 2‐oxo‐acid reductase of broad substrate specificity from two Proteus species

Proteus mirabilis and Proteus vulgaris contain in the crude extract a non‐pyridine nucleotide dependent reductase for 2‐oxo‐acids as well as 2‐oxo‐dicarboxylic acids of specific activities of 1–10 units/mg protein. The enzyme catalyzes the reduction of very different 2‐oxo‐acids to the corresponding (2R)‐hydroxy‐acid. Reduced methyl‐ or benzylviologen act as artifical electron donors. The membrane‐bound enzyme has been enriched 167‐fold to a purity 90% as judged by electrophoresis. It seems that the enzyme does not contain flavin.