Protein having nadh and/or nadph oxidase activity

A protein comprising an amino acid sequence of SEQ ID NO:1 which further contains at least one amino acid substitution selected from (a) to (g):

• (a) a substitution of Leu-42 with an amino acid having a side-chain surface area of 100 to 200 (Å2);
• (b) a substitution of Met-46 with a neutral amino acid having a side-chain surface area of not more than 150 (Å2) or an acidic amino acid having a side-chain surface area of not more than 150 (Å2);
• (c) a substitution of Asn-96 with a basic amino acid;
• (d) a substitution of Tyr-172 with an amino acid having a smaller side-chain surface area than Tyr;
• (e) a substitution of Thr-196 with a basic amino acid;
• (f) a substitution of Ala-312 with an amino acid having a larger side-chain surface area than Ala;
• and
• (g) a substitution of Phe-371 with an aliphatic amino acid, an acidic amino acid, or an amino acid having a hydroxyl group-bearing side chain, and
• contains the amino acid sequence of SEQ ID NO:1 except for the amino acid substitution.

An enzyme variant-containing product obtained by processing a culture of a transformant obtained by transformation of a host cell with a vector comprising an isolated DNA encoding a protein

• wherein said protein has NADH oxidase activity or NADPH oxidase activity or both and has improved stability compared to the protein having the amino acid sequence of SEQ ID NO:1, and
• which has an amino acid sequence that has at least 85% sequence identity to the amino acid sequence of SEQ ID NO:1 and further contains at least one amino acid substitution selected from (a) to (g):
• (a) a substitution of an amino acid residue at a position corresponding to position 42 of SEQ ID NO:
• 1 with an amino acid having a side-chain surface area of 100 to 200 Å2;
• (b) a substitution of an amino acid residue at a position corresponding to position 46 of SEQ ID NO:
• 1 with a neutral amino acid having a side-chain surface area of 100 to 150 Å2 or an acidic amino acid having a side-chain surface area of 100 to 150 Å2:
• (c) a substitution of an amino acid residue at a position corresponding to position 96 of SEQ ID NO:1 with a basic amino acid;
• (d) a substitution of an amino acid residue at a position corresponding to position 172 of SEQ ID NO:
• 1 with an amino acid having a smaller side-chain surface area than Tyr;
• (e) a substitution of an amino acid residue at a position corresponding to position 196 of SEQ ID NO:
• 1 with a basic amino acid;
• (f) a substitution of an amino acid residue at a position corresponding to position 312 of SEQ ID NO:
• 1 with an amino acid having a larger side-chain surface area than Ala;
• and
• (g) a substitution of an amino acid residue at a position corresponding to position 371 of SEQ ID NO:1 with an aliphatic amino acid, an acidic amino acid, or an amino acid having a hydroxyl group-bearing side chain.