Patent ID: 8609391

Claim:
A mannose-6-phosphate isomerase mutant enzyme, comprising at least one selected from the group consisting of: a) the mutant, in which the amino acid residue Arg (R), at position 142 in the mannose-6-phosphate isomerase having SEQ ID NO: 1 is replaced with to Asn (N); b) the mutant, in which the amino acid residues Lys (K), Ash (N), and Met (M), at positions 21, 74, and 134 in the mannose-6-phosphate isomerase as set forth in SEQ ID NO: 2 are replaced with Glu (E), Thr (T), and Arg (R), respectively; c) the mutant, in which the amino acid residues Glu (E) and Thr (T), at positions 67 and 238 in the mannose-6-phosphate isomerase as set forth in SEQ ID NO: 2 are replaced with Gly (G) and Ile (I), respectively; d) the mutant, in which the amino acid residue Lys (K), at position 124 in the mannose-6-phosphate isomerase as set forth in SEQ ID NO: 2 is replaced with Arg (R); e) the mutant, in which the amino acid residue Leu (L), at position 129 in the mannose-6-phosphate isomerase as set forth in SEQ ID NO: 2 is replaced with Phe (F) or Tyr (Y); f) the mutant of the mannose-6-phosphate isomerase selected from the group consisting of the mutants, in which the amino acid residue Asn (N), at position 90 in the mannose-6-phosphate isomerase as set forth in SEQ ID NO: 2 is replaced with Ala (A), Asp (D), His (H) or Leu (L); and g) the mutant, in which at least two residues are mutated in SEQ ID NO: 2 wherein at least one mutation is selected from those recited in the above b) to f).