EPR spectroscopic and computational characterization of the hydroxyethylidene-thiamine pyrophosphate radical intermediate of pyruvate:ferredoxin oxidoreductase.

ABSTRACT: The radical intermediate of pyruvate:ferredoxin oxidoreductase (PFOR) from Moorella thermoacetica was characterized using electron paramagnetic resonance (EPR) spectroscopy at X-band and D-band microwave frequencies. EPR spectra, obtained with various combinations of isotopically labeled substrate (pyruvate) and coenzyme (thiamine pyrophosphate (TPP)), were analyzed by spectral simulations. Parameters obtained from the simulations were compared with those predicted from electronic structure calculations on various radical structures. The g-values and 14N/15N-hyperfine splittings obtained from the spectra are consistent with a planar, hydroxyethylidene-thiamine pyrophosphate (HE-TPP) pi-radical, in which spin is delocalized onto the thiazolium sulfur and nitrogen atoms. The 1H-hyperfine spl

SUBMITTER: Mansoorabadi SO 

PROVIDER: S-EPMC2505060 | biostudies-literature | 2006 Jun

REPOSITORIES: biostudies-literature