Baker J R, Zyzak D V, Thorpe S R, Baynes J W
Department of Clinical Biochemistry, Green Lane Hospital, Auckland, New Zealand.
Clin Chem. 1993 Dec;39(12):2460-5.
We studied the chemistry of the fructosamine assay for glycated serum proteins by using the model Amadori compound N alpha-formyl-N epsilon-fructoselysine (fFL), an analog of glycated lysine residues in protein. Free lysine was formed at approximately 70% yield during a standard 20-min incubation of fFL with alkaline nitroblue tetrazolium (NBT) at 37 degrees C. Although superoxide dismutase (SOD; EC 1.15.1.1) and catalase (EC 1.11.1.6) decreased the yield of the product, monoformazan dye (MF+), the yield of MF+ was slightly greater under anaerobic than aerobic conditions, excluding a role for superoxide as an intermediate in the reduction of NBT during the fructosamine assay. SOD added to diabetic patients' sera at physiological concentrations also caused a significant (approximately 50%) inhibition of MF+ formation. This inhibition was reduced by addition of nonionic detergents, which contain organic peroxide inhibitors of SOD, to the fructosamine reagent. Overall, these data indicate that the Amadori compound is the direct reductant of NBT in the fructosamine assay and that superoxide is not an intermediate in the reaction. The inhibitory effects of SOD and catalase are most likely the result of oxygen regeneration in the assay mixture.
我们使用模型阿马多里化合物Nα-甲酰基-Nε-果糖赖氨酸（fFL）（蛋白质中糖化赖氨酸残基的类似物）研究了糖化血清蛋白果糖胺测定的化学过程。在37℃下将fFL与碱性硝基蓝四氮唑（NBT）进行标准20分钟孵育期间，游离赖氨酸以约70%的产率形成。尽管超氧化物歧化酶（SOD；EC 1.15.1.1）和过氧化氢酶（EC 1.11.1.6）降低了产物单甲臜染料（MF+）的产率，但在厌氧条件下MF+的产率略高于有氧条件，这排除了超氧化物在果糖胺测定中作为NBT还原中间体的作用。以生理浓度添加到糖尿病患者血清中的SOD也显著（约50%）抑制了MF+的形成。通过向果糖胺试剂中添加含有SOD有机过氧化物抑制剂的非离子洗涤剂，这种抑制作用得以降低。总体而言，这些数据表明在果糖胺测定中阿马多里化合物是NBT的直接还原剂，并且超氧化物不是该反应的中间体。SOD和过氧化氢酶的抑制作用很可能是测定混合物中氧气再生的结果。
