Ahmad R, Wu Z, Armstrong D A
Biochemistry. 1983 Apr 12;22(8):1806-10. doi: 10.1021/bi00277a010.
The kinetics of reaction of oxidized lumiflavin (F0) with the radicals .CO2(-), CH3CHOH, and (CH3)2COH have been investigated at pH 7 and 24 +/- 1 degree C by the pulse radiolysis technique. The radicals have been shown to react with lumiflavin with second-order rate constants of 36 +/- 4, 26 +/- 3, and 20 +/- 3 in units of 10(8) M-1 s-1, respectively. These rate constants are close to the diffusion limit. The main product in each case was the lumiflavin semiquinone radical FH.. By utilization of long pulses (approximately 100 mus), it was shown that the reaction FH. + .AH(alpha) leads to FH- + A(alpha) + H+ [.AH(alpha) = .CO2(-), CH3CHOH, or (CH3)2COH] proceeded for all three types of .AH(alpha) radical with second-order rate constants of 17 (+4,-3), 9 (+5,-3), and 9 (+4,-3), respectively, in the above units. The beta-carbon radical .CH2CH(OH)CH3 added to .FH, forming an alkylated flavin, while the .CH2CH2OH radical appeared to be capable of addition or hydrogen atom donation to .FH.
在pH 7和24±1℃条件下，采用脉冲辐解技术研究了氧化型黄素单核苷酸（F0）与自由基·CO2(-)、CH3CHOH和(CH3)2COH的反应动力学。结果表明，这些自由基与黄素单核苷酸反应的二级速率常数分别为36±4、26±3和20±3（单位为10(8) M-1 s-1）。这些速率常数接近扩散极限。每种情况下的主要产物都是黄素单核苷酸半醌自由基FH·。通过使用长脉冲（约100 μs），结果表明反应FH· + ·AH(α) → FH- + A(α) + H+ [·AH(α) = ·CO2(-)、CH3CHOH或(CH3)2COH]对所有三种类型的·AH(α)自由基都能进行，其二级速率常数分别为17（+4，-3）、9（+5，-3）和9（+4，-3）（单位同上）。β-碳自由基·CH2CH(OH)CH3加成到·FH上，形成烷基化黄素，而·CH2CH2OH自由基似乎能够加成到·FH上或向·FH提供氢原子。
