hexacoordination

— This stabilization was definitively confirmed by the spectral analysis of VPi showing a stable pentacoordinate high-spin heme-iron state at pH 3.5 and 7 characteristic of an active peroxidase [14 ], unlike what observed for the native enzyme, where the breakdown of the proximal histidine-iron interaction (at pH 3–3.5) and iron hexacoordination by proximal and distal histidines (at pH 7) was produced.