There are disclosed a reductase having good heat stability, which resulted
in decrease in reaction time and improvement of reaction efficiency.
Specifically, disclosed is an enzyme having an amino acid sequence of SEQ
ID NO:1 in which at least one of the amino acids of the positions 245 and
271 of the amino acid sequence of SEQ ID NO:1 is replaced with another
amino acid(s); a polynucleotide having a nucleotide sequence that encodes
the amino acid sequence of said reductase; a vector containing said
polynucleotide; a transformant containing said polynucleotide or said
vector, and the like.