Thermostable 1,5-anhydroglucitol dehydrogenase, and method for measurement of 1,5-anhydroglucitol by using the same

An isolated thermostable 1,5-anhydroglucitol dehydrogenase protein comprising (A) or (B):

• wherein (A) is the amino acid sequence of SEQ ID NO:
• 4 having at least one variation selected from variations consisting of an amino acid residue at position 4 changed from a glycine residue to an alanine residue, an amino acid residue at position 6 changed from a glutamine residue to a histidine residue, an amino acid residue at position 14 changed from a serine residue to a threonine residue, an amino acid residue at position 37 changed from an alanine residue to a threonine residue or an arginine residue, an amino acid residue at position 50 changed from a proline residue to a glutamine residue, an amino acid residue at position 67 changed from a glutamic acid residue to a glycine residue, an amino acid residue at position 80 changed from an asparagine residue to a tyrosine residue, an amino acid residue at position 93 changed from a valine residue to a methionine residue, an amino acid residue at position 156 changed from an arginine residue to a proline residue, an amino acid residue at position 164 changed from a leucine residue to a methionine residue, an amino acid residue at position 202 changed from an asparagine residue to an aspartic acid residue, an amino acid residue at position 235 changed from a threonine residue to an alanine residue, an amino acid residue at position 348 changed from an asparagine residue to a tyrosine residue, an amino acid residue at position 362 changed from a glycine residue to an arginine residue, and an amino acid residue at position 473 changed from a valine residue to an alanine residue;
• and
• wherein (B) is the amino acid sequence of (A) in which 1 to 10 amino acid residues are deleted, substituted, or added in addition to the variations found in the amino acid sequence of (A), wherein
• the isolated thermostable 1,5-anhydroglucitol dehydrogenase protein has 1,5-anhydroglucitol dehydrogenase activity and maintains 8% or more of its 1,5-anhydroglucitol dehydrogenase activity after heating at 45° C. for 10 minutes.