Patent ID: 6933365

Claim:
An isolated mutant tyrosine repressor, wherein the unmutated tyrosine repressor has an amino acid sequence that is at least 80% identical to SEQ ID NO: 2, said repressor having one or more mutations selected from the group consisting of: a) a replacement of the valine residue at position 67 corresponding to SEQ ID NO: 2 with an amino acid other than valine; b) a replacement of the tyrosine residue at position 72 corresponding to SEQ ID NO: 2 with an amino acid other than tyrosine; and c) a replacement of the aspartic acid residue at position 97 corresponding to SEQ ID NO: 2 with an amino acid other than aspartic acid; wherein the mutant tyrosine repressor has an increased positive regulatory activity for expression of tyrosine phenol lyase gene compared with the tyrosine repressor not having the one or more mutations, wherein the mutant tyrosine repressor is encoded by a DNA which hybridizes to SEQ ID NO: 1 under stringent conditions, and wherein said stringent conditions comprise 1×SSC, 01% SDS at 65° C.