Patent ID: 6946588

Claim:
An isolated or recombinant nucleic acid comprising a sequence encoding a threonine deaminase protein capable of catalyzing the conversion of threonine to α-ketobutyrate, wherein: a. the sequence encoding a leucine residue corresponding to amino acid position 447 in the protein encoded by SEQ ID NO:1 is replaced with a sequence encoding an alanine, isoleucine, valine, phenylalanine, tryptophan, or methionine residue; b. the sequence encoding a leucine residue corresponding to amino acid position 481 in the protein encoded by SEQ ID NO:1 is replaced with a sequence encoding an alanine, isoleucine, proline, phenylalanine, tryptophan, or methionine residue; or c. the sequences encoding leucine residues corresponding to amino acid positions 447 and 481 in the protein encoded by SEQ ID NO:1 are independently replaced with sequences encoding alanine, isoleucine, phenylalanine, tryptophan, or methionine residues.