Recombinant thermostable enzyme which forms non-reducing saccharide from reducing amylaceous saccharide

Abstract

Disclosed is a recombinant thermostable enzyme which has a molecular weight of about 69,000-79,000 daltons and a pI of about 5.4-6.4, and forms non-reducing saccharides having a trehalose structure as an end unit from reducing amylaceous saccharides having a degree of glucose polymerization of at least 3. The enzyme has satisfactorily high thermostability, i.e. it is substantially not inactivated even when incubated in an aqueous solution (pH 7.0) at 85° C. for 60 min, and this facilitates the production of such non-reducing saccharides on an industrial scale and in a satisfactorily-high yield.

What is claimed is:  
     
         1 . A purified recombinant thermostable enzyme having the following physicochemical properties: 
 (1) Action 
 Forming non-reducing saccharides having a trehalose structure as an end unit and having a degree of glucose polymerization of at least 3 from maltotetraose or reducing amylaceous saccharides having a degree of glucose polymerization of at least 3;  
   (2) Molecular weight 
 About 69,000-79,000 daltons on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE);  
   (3) Isoelectric point (pI) 
 About 5.4-6.4 on isoelectrophoresis;  
   (4) Thermostability 
 Substantially not inactivated even when incubated in an aqueous solution (pH 7.0) at 85° C. for 60 min.; and  
   (5) Amino acid sequence 
 An amino acid sequence which is not identical to SEQ ID NO:1 but is a functional equivalent thereof, and which contains one or more amino acid residues selected partially from SEQ ID NO:3 and SEQ ID NO:4.