Fructosyl peptide oxidase and utilization thereof

1. A method of defructosylating a fructosylated peptide or protein, comprising reacting the peptide or protein with an enzyme that is extracted from a plant of the genus Zingiber and exhibits defructosylation action.

2. The defructosylation method according to claim 1 , wherein the fructosylated peptide comprises the amino acid sequence of any of SEQ ID NOs: 1 to 5.

3. The defructosylation method according to claim 1 or claim 2 , wherein the fructosylated protein is hemoglobin A1 c.

4. An enzyme that exhibits defructosylation action on a fructosylated peptide or protein and is extracted from a plant of the genus Zingiber.

5. The enzyme according to claim 4 , wherein the enzyme has the following physical and chemical characteristics a) to h):

a) Action: in the presence of oxygen, acting on a fructosyl valine or fructosyl peptide wherein the fructosyl peptides may be selected from peptides comprising the amino acid sequences of SEQ ID NOs: 1 to 5, and catalyzing at least a reaction which produces corresponding valine or non-fructosyl peptide, glucosone, and hydrogen peroxide;

b) Optimum pH: 8.0 to 9.0;

c) Range of stable pH: pH 6.0 to 7.0;

d) Km value for fructosyl valyl histidine: 1.2 mM;

e) Range of optimum temperature: 60° C. or more;

f) Temperature stability: 80% or more of the enzyme activity remains after heat-treatment for 15 minutes at 50° C.; and

g) Molecular weight: approximately 27 kDa by gel filtration.

6. A method for measuring a fructosylated peptide or protein, comprising measuring at least one reaction product produced through the defructosylation method according to claim 1 or claim 2 .

7. The method for measuring a fructosylated-peptide or protein according to claim 6 , wherein the reaction product produced through the defructosylation method is hydrogen peroxide, glucosone, or a defructosyl peptide.