Rao A V, Islam N S, Ramasarma T
Department of Biochemistry, Indian Institute of Science, Bangalore, India.
Arch Biochem Biophys. 1997 Jun 15;342(2):289-97. doi: 10.1006/abbi.1997.0103.
Diglycyl triperoxodivanadate [V2O2(O2)3(Gly H)2(H2O)2], a synthetic compound with mu-peroxo-bridge derived from H2O2 and vanadate, oxidized bromide to a bromination-competent intermediate in phosphate buffer and physiological pH. This is in contrast to the requirement of acid medium with H2O2 as the oxidant. Addition of its solid to bromide solution instantly produced a 262-nm-absorbing compound that converted phenol red (a trap) to its 592-nm-absorbing bromo-derivative. The high bromination activity was lost on dissolving this compound in water and the solution showed the presence of peroxovanadates (mono and di) and vanadates (V1 and oligomeric V10) in 51V-NMR spectrum. Of these, diperoxovanadate and vanadate together supported slow bromination activity by a second set of reactions including bromide-assisted reductive formation of vanadyl. Bromination activity dependent on vanadyl was sensitive to oxidation by excess H2O2 and to complexation by EDTA, whereas that of triperoxodivanadate was relatively insensitive. Vanadyl and diperoxovanadate are capable of forming a mu-peroxo-bridged complex that is essentially similar to the synthetic vanadate dimer used in the present experiments. It appears that a mu-peroxo-intermediate is the proximal oxidant of bromide in vanadium-catalyzed bromoperoxidation.
双甘氨酰三过氧二钒酸盐[V2O2(O2)3(Gly H)2(H2O)2]是一种由过氧化氢和钒酸盐衍生而来的具有μ-过氧桥的合成化合物，在磷酸盐缓冲液和生理pH条件下能将溴化物氧化为具有溴化活性的中间体。这与以过氧化氢为氧化剂时需要酸性介质的情况形成对比。将其固体加入溴化物溶液中会立即产生一种在262nm处有吸收的化合物，该化合物能将酚红（一种捕获剂）转化为在592nm处有吸收的溴代衍生物。将该化合物溶解于水中时，其高溴化活性丧失，并且在51V核磁共振谱中溶液显示存在过氧钒酸盐（单过氧钒酸盐和双过氧钒酸盐）和钒酸盐（V1和低聚V10）。其中，双过氧钒酸盐和钒酸盐通过包括溴化物辅助的钒酰还原形成在内的第二组反应共同支持缓慢的溴化活性。依赖于钒酰的溴化活性对过量过氧化氢的氧化和EDTA的络合敏感，而三过氧二钒酸盐的溴化活性则相对不敏感。钒酰和双过氧钒酸盐能够形成一种μ-过氧桥连络合物，该络合物与本实验中使用的合成钒酸盐二聚体基本相似。似乎μ-过氧中间体是钒催化溴过氧化物酶反应中溴化物的近端氧化剂。
