Spectroscopic and electronic structure study of the enzyme-substrate complex of intradiol dioxygenases: substrate activation by a high-spin ferric non-heme iron site.

ABSTRACT: Various mechanisms have been proposed for the initial O(2) attack in intradiol dioxygenases based on different electronic descriptions of the enzyme-substrate (ES) complex. We have examined the geometric and electronic structure of the high-spin ferric ES complex of protocatechuate 3,4-dioxygenase (3,4-PCD) with UV/visible absorption, circular dichroism (CD), magnetic CD (MCD), and variable-temperature variable-field (VTVH) MCD spectroscopies. The experimental data were coupled with DFT and INDO/S-CI calculations, and an experimentally calibrated bonding description was obtained. The broad absorption spectrum for the ES complex in the 6000-31000 cm(-1) region was resolved into at least five individual transitions, assigned as ligand-to-metal charge transfer (LMCT) from the protocatechuate

SUBMITTER: Pau MY 

PROVIDER: S-EPMC2536531 | biostudies-literature | 2007 Feb

REPOSITORIES: biostudies-literature