Purified Brassica napus enoyl acyl carrier protein reductase (ENR) was used to select specific antibodies from a library of antibody fragments, single-chain F_v (scF_v), displayed on filamentous phage. Analysis of the selected clones by BstNl fingerprinting and nucleotide sequencing showed that the scF_v were derived from three different human V_H germline genes. The binding specificities were confirmed by Western blots and ELISA. The scF_v preparations reacted with B. napus ENR, but not with β-keto reductase, nor enoyl reductase from Escherichia coli. Analysis of fragments generated by CNBr treatment indicates that the scF_v 3.13 recognizes an epitope located within the n-terminal 80 amino acids of the enzyme molecule. The scF_v were used to detect ENR directly in extracts of B. napus seeds.