The interaction of fatty acid substrate (palmitate) and inhibitor (metyrapone: 2-methyl-1,2-di-3-pyridyl-1-propanone) with cytochrome P-450 BM3 was analysed by UV-visible and circular dichroism spectroscopy, and by surface-enhanced resonance Raman scattering (SERRS). While visible spectroscopy provides information on the relative affinities of these compounds, SERRS provides additional novel data indicating palmitate-induced structural changes in the haem environment. SERRS also demonstrates that binding of both palmitate and the large nitrogenous ligand metyrapone occurs simultaneously to P-450 BM3 — highlighting the usefulness of this technique in probing haemoprotein active sites.
