Oxo-molybdenum enzymes: New insights from metal and ligand hyperfine coupling

Abstract

Molybdenum-95, hydrogen-1, oxygen-17 and sulfur-33 hyperfine coupling constants are available via electron spin resonance for a number of oxo-molybdenum enzymes, and for xanthine oxidase in particular. The enzyme data is compared with complementary information obtained for a series of model complexes featuring quadridentate N2S2 ligands. The comparisons indicate thal MovOS(OR) and MovO(SH)(OR) (OR = bound product) are the centres responsible for the “Very Rapid” and “Rapid” ESR signals of xanthine oxidase. A MovO(OH) centre appears to be involved in the “Slow” ESR signal of xanthine oxidase and in the low pH forms of sulfite oxidase and the nitrate reductases. © 1990 IUPAC