Steviol glycoside hexose transferase and gene coding for same

Abstract

The purpose of the present invention is to provide a steviol glycoside hexose transferase, and a method for producing a steviol glycoside that contains glucose and/or rhamnose using said enzyme. The present invention provides a steviol glycoside hexose transferase, and a method for producing a steviol glycoside that contains glucose and/or rhamnose using said enzyme. The present invention also provides a transformant into which a steviol glycoside hexose transferase gene has been introduced, and a method for preparing said transformant.

What is claimed is: 
     
         1 . A protein according to any one selected from the group consisting of the following (a) to (c):
 (a) a protein consisting of the amino acid sequence of SEQ ID NO: 2;   (b) a protein consisting of an amino acid sequence wherein 1 to 48 amino acids other than the amino acid residue X 7  are deleted, substituted, inserted, and/or added in the amino acid sequence of SEQ ID NO: 2 and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the following formula (I);   (c) a protein having an amino acid sequence having a sequence identity of 90% or more to the amino acid sequence of SEQ ID NO: 2 wherein an amino acid corresponding to the amino acid residue X 7  is the same and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the following formula (I);   
       
         
           
           
               
               
           
         
         wherein R 1  represents H, a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, a C 4 -C 20  alkyldienyl group, a C 6 -C 18  aryl group, a C 6 -C 20  alkylaryl group, a C 6 -C 20  arylalkyl group, a C 4 -C 20  cycloalkyl group, a C 4 -C 20  cycloalkenyl group, a (C 3 -C 10  cycloalkyl)C 1 -C 10  alkyl group or a sugar residue. 
       
     
     
         2 . The protein according to  claim 1 , wherein the protein is
 (b′) a protein consisting of an amino acid sequence wherein 1 to 48 amino acids other than the amino acid residues X 1  to X 7  are deleted, substituted, inserted, and/or added in the amino acid sequence of SEQ ID NO: 2 and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the formula (I); or   (c′) a protein having an amino acid sequence having a sequence identity of 90% or more to the amino acid sequence of SEQ ID NO: 2 wherein amino acids corresponding to the amino acid residues X 1  to X 7  are the same and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the formula (I).   
     
     
         3 . The protein according to  claim 1 , wherein the hexose is selected from the group consisting of glucose or rhamnose. 
     
     
         4 . The protein according to  claim 1 , wherein the R 1  is H or a sugar residue of a glucose monomer or a glucose dimer. 
     
     
         5 . The protein according to  claim 1 , wherein the compound is steviolmonoside or rubusoside. 
     
     
         6 . A polynucleotide selected from the group consisting of the following (a) to (d):
 (a) a polynucleotide comprising the nucleotide sequence of SEQ ID NO: 1;   (b) a polynucleotide encoding a protein consisting of the amino acid sequences of SEQ ID NO: 2;   (c) a polynucleotide encoding a protein consisting of an amino acid sequence wherein 1 to 48 amino acids other than the amino acid residue X 7  are deleted, substituted, inserted, and/or added in the amino acid sequence of SEQ ID NO: 2 and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the following formula (I);   (d) a polynucleotide encoding a protein having an amino acid sequence having a sequence identity of 90% or more to the amino acid sequence of SEQ ID NO: 2 wherein an amino acid corresponding to the amino acid residue X 7  is the same and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by formula (I):   
       
         
           
           
               
               
           
         
         wherein R 1  represents H, a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, a C 4 -C 20  alkyldienyl group, a C 6 -C 18  aryl group, a C 6 -C 20  alkylaryl group, a C 6 -C 20  arylalkyl group, a C 4 -C 20  cycloalkyl group, a C 4 -C 20  cycloalkenyl group, a (C 3 -C 10  cycloalkyl)C 1 -C 10  alkyl group or a sugar residue. 
       
     
     
         7 . The polynucleotide according to  claim 6 , wherein the polynucleotide is
 (c′) a polynucleotide encoding a protein consisting of an amino acid sequence wherein 1 to 48 amino acids other than the amino acid residues X 1  to X 7  are deleted, substituted, inserted, and/or added in the amino acid sequence of SEQ ID NO: 2 and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the formula (I); or   (d′) a polynucleotide encoding a protein having an amino acid sequence having a sequence identity of 90% or more to the amino acid sequence of SEQ ID NO: 2 wherein amino acids corresponding to the amino acid residues X 1  to X 7  are the same and having an activity to add hexose at position 2 of glucose at position 13 in a compound represented by the formula (I).   
     
     
         8 . The polynucleotide according to  claim 6 , wherein the hexose is selected from the group consisting of glucose or rhamnose. 
     
     
         9 . The polynucleotide according to  claim 6 , wherein the R 1  is H or a sugar residue of a glucose monomer or a glucose dimer. 
     
     
         10 . The polynucleotide according to  claim 6 , wherein the compound is steviolmonoside or rubusoside. 
     
     
         11 . A non-human transformant in which the polynucleotide according to  claim 6  is introduced. 
     
     
         12 . The transformant according to  claim 11 , wherein the polynucleotide is inserted into an expression vector. 
     
     
         13 . The transformant according to  claim 11 , wherein the transformant is a plant. 
     
     
         14 . An extract of the transformant according to  claim 11 . 
     
     
         15 . A food or drink, a pharmaceutical product, or an industrial raw material comprising the extract according to  claim 14 .