Water and bromide in the active center of vanadate-dependent haloperoxidases

Two aqua-oxovanadium complexes, viz. [A-VO(H2O)( sal-L-Leu)] (1) and [VO(H2 O)(2)(5-Br-sal-Gly)]. H2O (2 . H2O), containing the water ligands in cis- a nd trans-positions to the oxo group at V-OH2 distances ranging from 2.008 t o 2.228 Angstrom, have been structurally characterized in order to model th e apical electron density feature found in the structures of fungal and alg al vanadate-dependent peroxidases. Br K-edge XAS of bromide-treated bromope roxidase from Ascophyllum nodosum and model compounds (including 2 . H2O) h as been used to show that the substrate bromide does not bind to active sit e vanadium but to a light atom, possibly carbon, in its vicinity. (C) 2000 Elsevier Science Inc. All rights reserved.