Saponin-decomposing enzyme, gene thereof and large-scale production system for producing soyasapogenol B

A method for producing soyasapogenol B, which comprises decomposing a glycoside having soyasapogenol B as an aglycone using a culture containing a protein having saponin-decomposing activity, which is obtained by transforming a host with a recombinant vector comprising a polynucleotide encoding a protein having saponin-decomposing activity, wherein said polynucleotide is selected from the group consisting of:

• (i) a polynucleotide consisting of the DNA sequence of SEQ ID NO:
• 1;
• (ii) a polynucleotide that has at least 95% homology to the polynucleotide of (i) and encodes a protein having saponin-decomposing activity, wherein the protein produces soyasapogenol B from saponin in a culture;
• (iii) a polynucleotide that hybridizes with the polynucleotide of (i) under stringent conditions and encodes a protein having saponin-decomposing activity, wherein said stringent conditions comprise two washes at 42° C. for 20 minutes each in 0.5×SSC, 0.4% SDS and 6M urea, and wherein the protein produces soyasapogenol B from saponin in a culture;
• (iv) a polynucleotide encoding a protein comprising the amino acid sequence of SEQ ID NO:
• 2;
• and
• (v) a polynucleotide encoding a protein that has at least 95% homology to the amino acid sequence of SEQ ID NO:
• 2 and having saponin-decomposing activity, wherein the protein produces soyasapogenol B from saponin in a culture.

A method for producing soyasapogenol B, which comprises decomposing a glycoside having soyasapogenol B as an aglycone using at least one isolated protein having saponin-decomposing activity selected from the group consisting of:

• (a) a protein comprising the amino acid sequence of SEQ ID NO:
• 2;
• (b) a protein that has at least 95% homology to the protein of (a) and having saponin-decomposing activity, wherein the protein produces soyasapogenol B from saponin;
• (c) a protein encoded by a polynucleotide consisting of the DNA sequence of SEQ ID NO:
• 1;
• (d) a protein encoded by a polynucleotide that has at least 95% homology to the polynucleotide of SEQ ID NO:
• 3 and having saponin-decomposing activity, wherein the protein produces soyasapogenol B from saponin;
• and
• (e) a protein encoded by a polynucleotide that hybridizes with the polynucleotide of SEQ ID NO:
• 1 under stringent conditions and encodes a protein having saponin-decomposing activity, wherein said stringent conditions comprise two washes at 42° C. for 20 minutes each in 0.5×SSC, 0.4% SDS and 6M urea, and wherein the protein produces soyasapogenol B from saponin in a culture.