The reaction of xanthine oxidase with molecular oxygen.

摘要: Abstract The reaction of reduced xanthine oxidase with oxygen occurs in two distinct kinetic phases the rate fast phase being about 10 times greater than that slow phase. Comparison transient state and steady kinetics demonstrates only oxidation is catalytically significant. time course quantitatively independent following factors: (a) activity to flavin ratio; (b) presence competitive inhibitors; (c) pretreatment enzyme either cyanide or allopurinol; (d) addition superoxide dismutase. Removal eliminates both reactivity molecular (Komai, H., Massey, V., Palmer, G. (1969) J. Biol. Chem. 244, 1692–1700). Both optical EPR data support interpretation 5 electrons are consumed 1 spectral properties slowly reacting species suggest residual electron present principally as iron-sulfur center II at pH 8.5. simplest requires rapid via fully observed for 1-electron a consequence poor small equilibrium concentration semiquinone. absence any effect dismutase on amount generated indicates hydrogen peroxide major product formed during oxidase.