Fluorescent biosensor for rapid determination of l-arginine

A fluorescent recombinant arginine deiminase (ADI) comprising a recombinant ADI comprising a polypeptide having an amino acid sequence that is at least 95% identical to SEQ ID NO:

• 1 or SEQ ID NO:
• 2, wherein the amino acid at position 251 of SEQ ID NO:
• 1 is not cysteine while the amino acid at position 265 of SEQ ID NO:
• 1 must be cysteine;
• and the amino acid at position 44 of SEQ ID NO:
• 2 must be cysteine while the amino acid at position 251 of SEQ ID NO:
• 2 is not cysteine, and a fluorescent dye covalently attached via an optional linker to the side chain of the cysteine at position 265 of SEQ ID NO:
• 1 or to the side chain of the cysteine at position 44 of SEQ ID NO:
• 2.