A protein, which is an aminoketone asymmetric reductase, having an effect of producing d-pseudoephedrine by acting on 1-2-methylaminopropiophenone, and having the following physiochemical properties:substrate: 1-2-methylaminopropiophenoneoptimum pH: pH 8.1optimum temperature: 55° C.coenzyme: NADPmolecular weight: about 28500 Da homotetramer and a nucleic acid coding the protein.