A novel iron-sulfur center in nitrile hydratase from Brevibacterium sp

We report that nitrile hydratase from Brevibacterium sp. contains a ferric ion in a biologically novel coordination environment. Nitrile hydratases are bacterial enzymes that catalyze the hydration of nitriles to amides. The best characterized is from Brevibacterium sp., strain R312, and is probably an alpha sub(2) beta sub(2) tetramer of 94,000 Da. The EPR spectrum of this protein is consistent with a rhombically distorted octahedral, low-spin ferric complex. We present resonance Raman and EXAFS spectra that suggest that the iron exists in a ligand field of sulfur and nitrogen or oxygen donor atoms.