Spectroscopic investigations of ferric cytochrome P-450-CAM ligand complexes. Identification of the ligand trans to cysteinate in the native enzyme.

Properties of an unusual heme cofactor in PLP-dependent cystathionine β-synthase

“…CBS as isolated, exhibits a rhombic EPR signal with g values of 2.5, 2.3 and 1.86, 18 which are similar to those of hemeproteins and model complexes with imidazole/thiolate ligands. [37][38][39][40][41] The narrow spacing between the g z and g x lines is typical of thiolate ligation. 41 The EPR spectrum of human CBS is unchanged between pH 6.0 and 9.0, indicating that the porphyrin ligands are insensitive to pH, at least over this range.…”

The binding of lignans, flavonoids and coumestrol to CYP450 aromatase: A molecular modelling study

“…(Sanderson et al, 2004) It has been shown that the coordination of oxygen to the heme iron produces a different type of change in absorption spectrum compared to nitrogen or sulphur coordination. (Dawson et al, 1982;White and Coon, 1982) The difference spectra measured for ANF, its metabolite 9-hydroxy-α-naphthoflavone (9-OH-ANF) and ENL indicate that the phytoestrogen replaces the natural substrate ASD from the active site and converts a high-spin iron into a low-spin iron producing a spectrum change typical for oxygen coordination to the iron. (Adlercreutz et al, 1993;Kellis and Vickery, 1984;Kellis et al, 1986;Kellis and Vickery, 1987) Additionally, two crystal structures of CYP450 enzymes show coordination from an oxygen to the heme iron (PDB entry codes 2CIX and 1NOO).…”

Iron Complexes of Flavonoids-Antioxidant Capacity and Beyond

“…Concordantly, the spectral changes (red shift in Soret band) indicated the flavonoid binding to the enzyme active site. Similarly spectral response (but significantly slower) was observed for cyclohexanone interaction with the heme moiety of cytochrome P-450 [116]. It is speculated that α-naphtolflavone structure represents an important structural motif for the aromatase inhibition.…”