Molecular modeling and mutational analysis (site-directed mutagenesis and saturation mutagenesis) were used to probe the molecular determinants of the substrate specificity of aminopyrrolnitrin oxygenase (PrnD) from Pseudomonas fluorescens Pf-5. There are 17 putative substrate-contacting residues, and mutations at two of the positions, positions 312 and 277, could modulate the enzyme substrate ...