A polypeptide according to any one of the following polypeptides (a) to (d): (a) a polypeptide consisting of the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing; (b) a polypeptide consisting of an amino acid sequence that has a deletion, a substitution, an insertion, and/or an addition of 1 or more amino acids with respect to the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing, and having activity to act on 1-benzyl-3-pyrrolidinone in the presence of an amino group donor to generate S-1-benzyl-3-aminopyrrolidine with optical purity of 93% e.e. or more; (c) a polypeptide consisting of an amino acid sequence that has 60% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing, and having activity to act on 1-benzyl-3-pyrrolidinone in the presence of an amino group donor to generate S-1-benzyl-3-aminopyrrolidine with optical purity of 93% e.e. or more; and (d) a polypeptide consisting of an amino acid sequence that has 60% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing, having activity to act on 1-benzyl-3-pyrrolidinone in the presence of an amino group donor to generate S-1-benzyl-3-aminopyrrolidine with optical purity of 93% e.e. or more, and wherein the polypeptide of (d) above has the following properties and/or: substrate specificity: (a) amino group donor: it exhibits activity for S-1-phenethylamine, benzylamine, and ±2-butylamine and does not exhibit activity for β-alanine and 4-aminobutyric acid; (b) amino group receptor: it exhibits activity for pyruvic acid and activity for glyoxalic acid; and/or B resistance to water-soluble organic solvent: it retains residual activity after 2 hours of treatment with any one of 1-propanol, 2-propanol, and acetone having a final concentration of 80%v/v equivalent to 10% or more of total activity before treatment. (a) a polypeptide consisting of the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing; (b) a polypeptide consisting of an amino acid sequence that has a deletion, a substitution, an insertion, and/or an addition of 1 or more amino acids with respect to the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing, and having activity to act on 1-benzyl-3-pyrrolidinone in the presence of an amino group donor to generate S-1-benzyl-3-aminopyrrolidine with optical purity of 93% e.e. or more; (c) a polypeptide consisting of an amino acid sequence that has 60% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing, and having activity to act on 1-benzyl-3-pyrrolidinone in the presence of an amino group donor to generate S-1-benzyl-3-aminopyrrolidine with optical purity of 93% e.e. or more; and (d) a polypeptide consisting of an amino acid sequence that has 60% or more sequence identity with the amino acid sequence shown in SEQ ID NO: 1 in the sequence listing, having activity to act on 1-benzyl-3-pyrrolidinone in the presence of an amino group donor to generate S-1-benzyl-3-aminopyrrolidine with optical purity of 93% e.e. or more, substrate specificity: (a) amino group donor: it exhibits activity for S-1-phenethylamine, benzylamine, and ±2-butylamine and does not exhibit activity for β-alanine and 4-aminobutyric acid; (b) amino group receptor: it exhibits activity for pyruvic acid and activity for glyoxalic acid; and/or (a) amino group donor: it exhibits activity for S-1-phenethylamine, benzylamine, and ±2-butylamine and does not exhibit activity for β-alanine and 4-aminobutyric acid; (b) amino group receptor: it exhibits activity for pyruvic acid and activity for glyoxalic acid; and/or B resistance to water-soluble organic solvent: it retains residual activity after 2 hours of treatment with any one of 1-propanol, 2-propanol, and acetone having a final concentration of 80%v/v equivalent to 10% or more of total activity before treatment.