Cytochrome P450 (P450) species play an important role in the metabolism of xenobiotics, and assaying the activities of P450 is important for evaluating the toxicity of chemicals in drugs and food. However, the lag time caused by the introduction and mixing of sample solutions can become sources of error as the throughput is heightened by increasing the sample number and decreasing the sample volume. To amend this technological obstacle, we developed a methodology to photoregulate the activity of P450 by using photoprotected (caged) compounds. We synthesized caged molecules of nicotinamide adenine dinucleotide phosphate (NADP+) and glucose 6-phosphate (G6P), which are involved in the generation of NADPH (cofactor of P450). The use of caged-G6P completely blocked the P450 catalysis before the UV illumination, whereas caged-NADP+ resulted in a little background reaction. Upon UV illumination, more than 90% of the enzymatic activity could be restored. The use of caged-G6P enabled assays in isolated microchambers (width, 50 μm; height, 50 μm) by encapsulating necessary ingredients in advance and initiating the reaction by UV illumination. The initiation of enzymatic reaction could be observed in a single microchamber. Minimizing uncertainties caused by the introduction and mixing of solutions led to significantly reduced errors of obtained kinetic constants.
细胞色素 P450(P450)物种在异种
生物的代谢过程中发挥着重要作用,而检测 P450 的活性对于评估药物和食品中
化学物质的毒性非常重要。然而,随着样品数量的增加和样品量的减少,样品溶液的引入和混合所造成的滞后时间会成为误差的来源。为了克服这一技术障碍,我们开发了一种使用光保护(笼状)化合物对 P450 的活性进行光调节的方法。我们合成了烟酰胺
腺嘌呤二核苷酸
磷酸(
NADP+)和 6-
磷酸葡萄糖(G6P)的笼状分子,它们参与生成
NADPH(P450 的辅助因子)。在紫外线照射前,使用笼装 G6P 可完全阻断 P450 的催化反应,而笼装
NADP+ 则会导致少量的背景反应。紫外线照射后,90% 以上的酶活性得以恢复。使用笼式-G6P 可以在隔离的微室(宽 50 μm;高 50 μm)中进行测定,方法是提前封装必要的成分,并通过紫外线照射启动反应。在一个微室中就能观察到酶反应的起始过程。尽量减少溶液的引入和混合所造成的不确定性,大大降低了所得动力学常数的误差。