Chemical and enzymatic properties of riboflavin analogues.
Chemical and enzymatic properties of riboflavin analogues.
复制标题
核黄素类似物的化学和酶学特性。
作者：
C. Walsh;J. Fisher;R. Spencer;D. Graham;W. Ashton;J. E. Brown;R. Brown;E. Rogers
本文介绍了26种核黄素类似物的化学性质和酶学性质。这些类似物包括氧化还原电位为-370至-128 mV的内环和外环取代的异咯嗪。物理和化学数据，如电子吸收光谱，pKas，和氧化还原电位的类似物，并讨论相对于优选的互变异构体和共振形式。像核黄素一样，大多数类似物被证明是二氢-5-脱氮黄素的催化氧化剂。已定量测定了与卵白色结合载脂蛋白结合的抗体，并用于确定该蛋白结合位点特异性的来源。发现几乎所有具有D-核糖基的类似物都被产氨短杆菌的黄素激酶/FAD合成酶系统加工至FAD水平。最广泛研究的是类似物与哈氏Beneckea harveyi的NAD（P）H：黄素氧化还原酶的反应性。许多类似物在这种酶促氧化还原反应中是底物，并且可以看到线性自由能-速率关系（log Vmax与类似物的E0'）与二氢-5-脱氮黄素的非酶促氧化中的类似关系平行。这表明了核黄素、5-脱氮核黄素和1-脱氮核黄素等不同黄素的反应的共同机制。
The chemical and enzymatic properties of 26 analogues of riboflavin are presented. These analogues include both endo- and exocyclically substituted isoalloxazines with redox potentials from -370 to -128 mV. Physical and chemical data such as the electronic absorption spectra, pKas, and redox potentials of the analogues are presented and are discussed with respect to preferred tautomeric and resonance forms. Like riboflavin, most of the analogues are shown to be catalytic oxidants of dihydro-5-deazaflavins. Analogue binding to egg white binding apoprotein has been quantitated and serves to determine the origins of binding site specificity for this protein. Nearly all of the analogues that possess D-ribityl groups are found to be processed to the FAD level by the flavokinase/FAD synthetase system of Brevibacterium ammoniagenes. Most extensively studied are the reactivities of the analogues with the NAD(P)H:flavin oxidoreductase of Beneckea harveyi. Many of the analogues are substrates in this enzymatic redox reaction, and a linear free energy-rate relation (log Vmax vs. E0' of the analogue) is seen that parallels similar relationships in the nonenzymatic oxidation of dihydro-5-deazaflavins. This suggests a common mechanism for the reactions of such diverse flavins as riboflavin, 5-deazariboflavin, and 1-deazariboflavin.