HIGH FREQUENCY CRYOGENIC EPR STUDY OF METHYLMALONYL COA MUTASE ENZYME

甲基丙二酰辅酶A的X-带EPR研究 班纳吉的实验室显示出相当混乱的光谱， 代表两个不同物种的贡献（JBC，1995年， 270：9295; JACS，1995，117：7033）。 该系统需要额外的 信息进行明确的解释。 Banerjee集团已经 与催化中间体相关的60 - 80 μ M自旋， 其交叉g值为2.11。 通过选择性同位素 取代研究中，信号推断显示双自由基 具有交换偶联的Co（II）-有机基团的中间体 汇率 这是一个稳态样本，他们从来没有能够 得到大于0.4自旋/摩尔的酶。 高场EPR正在 希望我们能把信号分开， 最终模拟光谱。 样品处理具有挑战性，因为 酶必须在冷冻前进行厌氧处理， 毛细管样品管难以装载、运输、冷冻保存， 状态，并在不解冻的情况下将艾德装入光谱仪， 污染. 不过，正在取得进展，初步 在IERC获得了Q带和W带的光谱。 这 该项目将在1998年继续进行。

X-band EPR studies on methylmalonyl-CoA mutase in Prof. Banerjee's laboratory show rather messy-looking spectra that seems to represent contributions from two separate species (JBC, 1995, 270:9295; JACS, 1995, 117:7033). This system requires additional information for a definitive interpretation. The Banerjee group has between 60 and 80 uM spin associated with the catalytic intermediate, which has a crossover g value at 2.11. By selective isotope substitution studies, the signals are deduced to show a biradical intermediate which has an exchange coupled Co(II)-organic radical pair. This is a steady-state sample, and they have never been able to get more than 0.4 spin/mol of enzyme. High-field EPR is being undertaken with the hope that we can separate the signals and eventually simulate the spectra. Sample handling is challenging, as the enzyme must be handled anaerobically prior to freezing, and the capillary sample tubes are difficult to load, ship, preserve in frozen state, and load ed into the spectrometer without thawing or contamination. Nevertheless, progress is being made, and preliminary Q-band and W-band spectra have been obtained at the IERC. This project will continue in 1998.