T. Borowski et al., First principle calculations for the non-heme iron centers of lipoxygenases: Geometrical and spectral properties, J PHYS CH B, 105(48), 2001, pp. 12212-12220
Lipoxygenases (LOs), which are non-heme-iron-containing enzymes, play a vit
al role in plant and mammalian organisms. Their active sites have been prob
ed by various spectroscopic techniques both in resting (Fe2+) and active (F
e3+) forms. Several crystal structures have been reported for ferrous forms
of LOS; nevertheless, many unresolved questions have still remained. In pa
rticular, subtle differences in the first coordination sphere of the iron c
enter seem to be very important for their catalytic activity thus any infor
mation about details of these structures is of great value. In this report,
we present results of first principle calculations for reliable models of
ferrous and ferric active sites of LOs undertaken to resolve ambiguities in
structure of both resting and active forms of the iron sites in lipoxygena
ses. Geometrical parameters of optimized models are compared with crystallo
graphic and EXAFS data. Time-dependent density functional theory (TDDFT) re
sults for spectroscopic states are confronted with the relevant experimenta
l results to validate the models and to gain an insight into the electronic
structure of ferric and ferrous active sites. Overall good agreement betwe
en the calculated and experimental positions of the absorption bands is fou
nd, and where possible, the sources of discrepancies are discussed.