Disclosed are: a recombinant C-terminal α-amidated enzyme derivative which lacks the formation of at least one disulfide bond among five disulfide bonds occurring in a C-terminal α-amidated enzyme derived from Xenopus laevis; DNA encoding the derivative; an expression vector carrying the DNA; a bacterium Escherichia coli transformed with the expression vector; and a method for producing the derivative by using the bacterium Escherichia coli.