Volk K J, Yost R A, Brajter-Toth A
Department of Chemistry, University of Florida, Gainesville 32611.
J Pharm Biomed Anal. 1990;8(2):205-15. doi: 10.1016/0731-7085(90)80028-n.
The enzymatic and electrochemical oxidation pathways of uric acid were determined on-line with thermospray-tandem mass spectrometry. Products and intermediates formed as a result of electrooxidation were monitored as the electrode potential was varied. Electrochemical results served as a model for the enzymatic studies. In fact, electrochemical studies were essential for elucidating the structures of intermediates because of the high conversion efficiencies in electrooxidation. Products and intermediates formed as a result of enzymatic oxidation of uric acid were monitored as the reaction time was varied. When the enzymatic oxidation of uric acid with peroxidase and H2O2 was studied, the same intermediates and products were observed as in the electrochemical oxidation. The tandem mass spectrometric results provide convincing evidence that the primary intermediate produced during both the enzymatic and electrochemical oxidation of uric acid has a quinonoid diimine structure. The primary intermediate can follow three distinct reaction pathways to produce the identified final products. The final enzymatic and electrochemical oxidation products observed in these studies were urea, CO2, alloxan, alloxan monohydrate, allantoin, 5-hydroxyhydantoin-5-carboxamide and parabanic acid.
采用热喷雾串联质谱法在线测定尿酸的酶促氧化途径和电化学氧化途径。随着电极电位的变化，监测电氧化过程中形成的产物和中间体。电化学结果为酶促研究提供了模型。事实上，由于电氧化过程中的高转化效率，电化学研究对于阐明中间体的结构至关重要。随着反应时间的变化，监测尿酸酶促氧化过程中形成的产物和中间体。在用过氧化物酶和过氧化氢研究尿酸的酶促氧化时，观察到与电化学氧化中相同的中间体和产物。串联质谱结果提供了令人信服的证据，表明尿酸酶促氧化和电化学氧化过程中产生的主要中间体具有醌二亚胺结构。主要中间体可以通过三种不同的反应途径生成已鉴定的最终产物。在这些研究中观察到的最终酶促氧化和电化学氧化产物为尿素、二氧化碳、尿囊素、尿囊素一水合物、尿囊酸、5-羟基乙内酰脲-5-甲酰胺和丙二酰脲。
