Murakami K, Onoda Y, Kimura J, Yoshino M
Department of Biochemistry, Aichi Medical University, Japan.
Biochem Mol Biol Int. 1997 Aug;42(5):1063-9. doi: 10.1080/15216549700203521.
Oxidative inactivation of AMP deaminase and its protection were analyzed under the in situ conditions of yeast cells. AMP deaminase was readily inactivated by an exposure to hydrogen peroxide plus copper in permeabilized yeast cells. Addition of ascorbic acid further enhanced the inactivation of the enzyme, suggesting the hydroxyl radical produced by the Fenton reaction is responsible for the inactivation of the enzyme. Addition of histidine caused an effective protection against the inactivation of AMP deaminase by hydrogen peroxide-induced hydroxyl radical. The concentration of histidine required for half-maximal effect was within physiological range. Cysteine showed less effective protection against oxidative inactivation. Other amino acids as potent copper-chelating agents as well as trolox and taurine showed little or no effect. Histidine can act as a physiological "antioxidant" in yeast cells.
在酵母细胞的原位条件下分析了AMP脱氨酶的氧化失活及其保护作用。在通透化的酵母细胞中，暴露于过氧化氢加铜会使AMP脱氨酶容易失活。添加抗坏血酸进一步增强了该酶的失活，表明芬顿反应产生的羟基自由基是该酶失活的原因。添加组氨酸可有效保护AMP脱氨酶免受过氧化氢诱导的羟基自由基的失活作用。产生半最大效应所需的组氨酸浓度在生理范围内。半胱氨酸对氧化失活的保护作用较弱。其他作为强铜螯合剂的氨基酸以及生育三烯酚和牛磺酸几乎没有作用或没有作用。组氨酸可以在酵母细胞中作为一种生理性“抗氧化剂”。
