A peptide comprising an Acetyl CoA carboxylase (ACCase) having a deleted biotin binding domain, having a deleted carboxy transferase domain, and having a functional biotin carboxylase (BC) domain is described. A nucleic acid that encodes the peptide described above and a recombinant host cell that contains the nucleic acid and expresses the encoded peptide is also described. A method of identifying Acetyl CoA carboxylase inhibitors, fungicides, and herbicides is also described herein.