Ravishankar H N, Ramasarma T
Department of Biochemistry, Indian Institute of Science, Bangalore.
Arch Biochem Biophys. 1995 Jan 10;316(1):319-26. doi: 10.1006/abbi.1995.1043.
Oxygen release accompanying oxidation of vanadyl by diperoxovanadate was suppressed on addition of NADH. The added NADH was rapidly oxidized, oxygen in the medium was consumed, and the reaction terminated on exhaustion of either NADH or vanadyl. The consumption of oxygen and disappearance of NADH needed small concentrations of diperoxovanadate to initiate and increased with increase in the concentration of vanadyl and NADH or decrease of pH. The products of the reaction were found to be NAD+ from NADH and vanadate oligomers from vanadyl and oxygen. The reaction was insensitive to catalase and was not dependent on H2O2. The reaction was inhibited by superoxide dismutase, cytochrome c, EDTA, Mn2+, histidine, and DMPO, but not by hydroxyl radical scavengers such as ethanol and benzoate. The ESR spectrum of the reaction mixture showed the presence of the 1:2:2:1 quartet signal typical of a DMPO-OH adduct, but this was not modified by ethanol. This oxygen radical species, possibly of .OV type derived from diperoxovanadate, is proposed to have a role in the reactions of oxygen release and NADH oxidation.
添加NADH后，过氧钒酸根氧化氧钒伴随的氧释放受到抑制。添加的NADH迅速被氧化，培养基中的氧被消耗，当NADH或氧钒耗尽时反应终止。氧的消耗和NADH的消失需要低浓度的过氧钒酸根来引发，并且随着氧钒和NADH浓度的增加或pH值的降低而增加。发现反应产物是NADH氧化生成的NAD⁺以及氧钒和氧生成的钒酸盐低聚物。该反应对过氧化氢酶不敏感，且不依赖于H₂O₂。该反应受到超氧化物歧化酶、细胞色素c、EDTA、Mn²⁺、组氨酸和DMPO的抑制，但不受乙醇和苯甲酸盐等羟基自由基清除剂的抑制。反应混合物的电子顺磁共振光谱显示存在典型的DMPO-OH加合物的1:2:2:1四重峰信号，但乙醇对此没有影响。这种氧自由基物种，可能源自过氧钒酸根的.OV类型，被认为在氧释放和NADH氧化反应中起作用。
