Theoretical characterization of the "very rapid" Mo(V) species generated in the oxidation of xanthine oxidase.
Density functional theory calculations of the "very rapid" Mo(V) intermediate of xanthine oxidase (XO) result in a square pyramidal geometry with end-on coordination of the model substrate. The Mo-C8 distance is 3.18 A, longer than previously reported from ENDOR experiments (<2.4 A Howes; et al. Biochemistry 1996, 35, 1432; 2.7-2.9 A Mandikandan; et al. J. Am. Chem. Soc. 2001, 123, 2658). Theoretical gas-phase isotropic hyperfine coupling constants A(iso)(C8) (B3LYP/BSII, 7.68 MHz; B3P86/BSII, 8.64 MHz) compare well with experimental values for the "very rapid" Mo(V) intermediate of XO with xanthine (8.8 MHz, Howes et al.) and 2-hydroxy-6-methylpurine (7.9 MHz, Mandikandan et al.). Absolute values of A(iso) of the metal-bound substrate oxygen are similar in magnitude to that of experiment.
Bayse
Craig A
CA
Department of Chemistry and Biochemistry, Old Dominion University, Hampton Boulevard, Norfolk, Virginia 23529, USA. cbayse@odu.edu
D001665:Binding Sites; D008956:Models, Chemical; D008982:Molybdenum / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D014969:Xanthine Oxidase / Q000737:chemistry* / Q000378:metabolism*
D008982:Molybdenum; D014969:Xanthine Oxidase