Okada Y, Okajima H
School of Health Sciences, Kyorin University, Hachioji, Japan.
Free Radic Res. 1995 Sep;23(3):273-85. doi: 10.3109/10715769509064040.
The influence of fatty acid (FA) micelles on cytochrome c(cyt.c) reduction and nitroblue tetrazolium (NBT) reduction assays for SOD activity, which continue to be widely used, has been studied. In the presence of FA micelles, the use of cyt.c reduction assay was found to overestimate the real activity of SOD. This effect is attributed to the following reasons. 1. The FA micelles lead to the denaturation of cyt.c, which gives rise to suppression of the reactivity of ferricyt.c(cyt.c(ox)) towards O2-. Furthermore, this denaturation increases the reoxidation rate of ferrocyt.c, and consequently the reoxidation causes a decreased rate of cyt.c(ox) reduction. 2. Positively charged cyt.c(ox) interacts with negatively charged FA micelles, and so cyt.c(ox) on the surface of FA micelles reacts less with negatively charged O2- because of electrostatic repulsion. Also in NBT reduction assay using a positively charged probe molecule, FA micelles cause the appearance of enhancement of SOD activity, due to suppression of the reactivity of NBT towards O2- by electrostatic repulsion. However, in both chemiluminescence assay using the uncharged probe molecule and LDH-NADH assay using the negatively charged probe molecule, FA micelles cannot influence the assays of the SOD activity, because the micelles do not interact electrostatically with probe molecules.
脂肪酸（FA）胶束对仍在广泛使用的细胞色素c（cyt.c）还原法和用于超氧化物歧化酶（SOD）活性的硝基蓝四唑（NBT）还原法的影响已得到研究。发现在存在FA胶束的情况下，使用cyt.c还原法会高估SOD的实际活性。这种影响归因于以下原因。1. FA胶束导致cyt.c变性，从而抑制了高铁细胞色素c（cyt.c(ox)）对O2-的反应性。此外，这种变性增加了亚铁细胞色素c的再氧化速率，因此再氧化导致cyt.c(ox)还原速率降低。2. 带正电荷的cyt.c(ox)与带负电荷的FA胶束相互作用，因此由于静电排斥，FA胶束表面的cyt.c(ox)与带负电荷的O2-反应较少。同样，在使用带正电荷的探针分子的NBT还原法中，由于静电排斥抑制了NBT对O2-的反应性，FA胶束导致SOD活性增强。然而，在使用不带电荷的探针分子的化学发光法和使用带负电荷的探针分子的LDH-NADH法中，FA胶束不会影响SOD活性的测定，因为胶束不会与探针分子发生静电相互作用。
