Method of degrading hardly degradable protein

1. A method for detoxifying a pathogenic prion protein, comprising the step of bringing a surface which may be contaminated with a pathogenic prion protein into contact with an enzyme exhibiting an activity of digesting a protein highly resistant to denaturation and degradation and having the following properties:

(a) activity and substrate specificity: hydrolyzing a peptide bond of a protein highly resistant to denaturation and degradation;

(b) molecular weight: 31,000 (determined by an SDS-polyacrylamide gel electrophoresis using a homogeneous gel having a gel concentration of 12%);

(c) isoelectric point: pI 9.3 (determined by polyacrylamide gel isoelectric focusing electrophoresis);

(d) optimum pH: pH 9.0 to 10.0; and

(e) optimum temperature for activity: 60 to 70° C.,

wherein the contacting step is carried out without preheating the subject, and said enzyme is produced by Bacillus licheniformis MSK-103 (FERM BP-08487).

2. The method according to claim 1 , wherein the contacting step is carried out without preheating the subject at 90° C. or more.

3. The method according to claim 1 , wherein the enzyme has the following property:

(g) exhibiting an activity of 2 U/g or more as the activity of digesting a protein highly resistant to denaturation and degradation (determined as an activity of digesting keratin azure).

4. The method according to claim 1 , wherein the enzyme is selected from the group consisting of

(X) an enzyme comprising the amino acid sequence of SEQ ID NO: 2;

(Y) a modified enzyme exhibiting an activity of digesting a protein highly resistant to denaturation and degradation, and comprising an amino acid sequence in which one or plural amino acids are deleted, substituted, or added in the amino acid sequence of SEQ ID NO: 2; and

(Z) a homologous enzyme exhibiting an activity of digesting a protein highly resistant to denaturation and degradation, and comprising an amino acid sequence having an 85% or more homology with the amino acid sequence of SEQ ID NO: 2.

5. The method according to claim 1 , wherein the protein highly resistant to denaturation and degradation is a pathogenic prion protein.

6. The method according to claim 3 , wherein the contacting step is carried out without preheating the subject at 90° C. or more.

7. The method according to claim 4 , wherein the contacting step is carried out without preheating the subject at 90° C. or more.

8. The method according to claim 5 , wherein the contacting step is carried out without preheating the subject at 90° C. or more.