The present invention relates to a protein which can asymmetrically reduce an ortho-substituted phenylglyoxalic acid compound to produce an amide or ester compound of corresponding optically-active ortho-substituted mandelic acid compound with a good optical yield, a DNA encoding the protein, a process for producing the protein from the DNA, and a process for asymmetrically reducing an ortho-substituted phenylglyoxalic acid compound to produce a corresponding optically-active ortho-substituted mandelic acid compound.