Publications by authors named "Irene Ogutu"
Two conserved second-sphere βArg (R) residues in nitrile hydratases (NHase), that form hydrogen bonds with the catalytically essential sulfenic and sulfinic acid ligands, were mutated to Lys and Ala residues in the Co-type NHase from Pseudonocardia thermophila JCM 3095 (PtNHase) and the Fe-type NHase from Rhodococcus equi TG328-2 (ReNHase). Only five of the eight mutants (PtNHase βR52A, βR52K, βR157A, βR157K and ReNHase βR61A) were successfully expressed and purified. Apart from the PtNHase βR52A mutant that exhibited no detectable activity, the k values obtained for the PtNHase and ReNHase βR mutant enzymes were between 1.
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- The metal binding motif in nitrile hydratases (NHases) is conserved and characterized by the sequence CXXCSCX in the α-subunit, with a synthesized peptide (VCTLCSCY) shown to coordinate Fe(II) under anaerobic conditions.
- EPR analysis confirmed the presence of an integer-spin signal in the Fe(II)-peptide complex, suggesting it has a distinct electronic structure with small axial zero-field splitting (ZFS).
- Exposure to air leads to changes in the EPR signals, indicating a transition from high-spin to low-spin Fe forms, revealing a novel progression of iron oxidation in NHases that includes both high-spin and low-spin states.