Peroxidase-benzhydroxamic acid complexes: spectroscopic evidence that a Fe-H2O distance of 2.6 angstrom can correspond to hexa-coordinate high-spin heme

Resonance Raman (RR) spectra have been obtained for single-crystal horserad ish peroxidase isozyme C complexed with benzhydroxamic acid (BHA). The data are compared with those obtained in solution by both RR and electronic abs orption spectroscopies at room and low (12-80 K) temperatures. Moreover, th e analysis has been extended to the Coprinus cinereus peroxidase complexed with BHA. The results obtained for the two complexes are very similar and a re consistent with the presence of an aqua six-coordinate high-spin heme. T herefore it can be concluded that despite the rather long Fe-H2O distance o f 2.6-2.7 Angstrom found by X-ray crystallography in both complexes, the di stal water molecule can still coordinate to the heme iron.