Uematsu Kohei, Ueno Takaaki, Kawasaki Haruka, Maruyama Chitose, Hamano Yoshimitsu, Katano Hajime
Department of Bioscience, Fukui Prefectural University.
Anal Sci. 2018;34(2):143-148. doi: 10.2116/analsci.34.143.
Previously, we reported that ε-poly-L-lysine (25 - 35 residues) significantly promoted a glucose oxidase enzymatic (GOx) reaction using ferricyanide ion as the oxidant, and that the effect was due to the formation of a polyion complex between anionic GOx and protonated (polycationic) ε-poly-L-lysine. Here, we show that streptothricins (STs), which have an L-β-lysine oligomer (1 - 7 residues) and possess only several positive charges at most, also effectively promote the GOx enzymatic reaction. Interestingly, the promotion effect increased with the size of the lysine oligomer of STs, suggesting that the ionic valence is a key factor determining the degree of the promotion effect. The GOx enzymatic reaction is accompanied by a color change due to the reduction of yellow ferricyanide ion to a colorless reductant. A more distinctive color change can be achieved by the addition of Fe(III) ions due to the formation of Prussian blue. Thus, the promotion effect allowed for colorimetric detection of STs at the 1 mg/L level. The detection method was simple and easy to carry out, and would become a helpful tool for the detection of STs.
此前，我们报道了ε-聚-L-赖氨酸（25 - 35个残基）以铁氰化物离子作为氧化剂时能显著促进葡萄糖氧化酶（GOx）的酶促反应，且该效应归因于阴离子型GOx与质子化（聚阳离子型）ε-聚-L-赖氨酸之间形成了聚离子复合物。在此，我们表明，链丝菌素（STs）具有L-β-赖氨酸低聚物（1 - 7个残基）且最多仅带有几个正电荷，它同样能有效促进GOx的酶促反应。有趣的是，促进效应随着STs赖氨酸低聚物的大小而增加，这表明离子价是决定促进效应程度的关键因素。GOx酶促反应伴随着颜色变化，这是由于黄色的铁氰化物离子还原为无色的还原剂。由于形成了普鲁士蓝，添加Fe(III)离子可实现更明显的颜色变化。因此，这种促进效应使得能够在1 mg/L水平比色检测STs。该检测方法简单易行，将成为检测STs的有用工具。
