Abstract
Ferrochelatase catalyzes Fe2+ insertion into porphyrins, and is inhibited by Hg2+. Resonance Raman spectra of mesoporphyrin IX show that binding to ferrochelatase restricts the conformation of the propionate side chains, but does not perturb the ring conformation. However, a pronounced perturbation is seen in the ternary complex with Hg2+. Several additional RR bands are activated, including some arising from [R-active vibrations, establishing loss of an effective symmetry center. Out-of-plane modes appear in the low frequency region. The strongest of these bands, γ5 and γ6, correspond to pyrrole tilting vibrations, which are in the same symmetry class as a doming distortion of the porphyrin. All four pyrrole N atoms are pointing toward the same side of the porphyrin plane, a geometry expected to facilitate Fe2+ insertion. This distortion is proposed to result from occupation of a metal-binding site, proximate to the prophyrin, which promotes insertion of Fe2+, while occupation by Hg2+ is inhibitory.
Original language | English (US) |
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Pages (from-to) | 12170-12174 |
Number of pages | 5 |
Journal | Journal of the American Chemical Society |
Volume | 119 |
Issue number | 50 |
DOIs | |
State | Published - Dec 17 1997 |
Externally published | Yes |
ASJC Scopus subject areas
- Catalysis
- General Chemistry
- Biochemistry
- Colloid and Surface Chemistry