Sabeh F, Wright T, Norton S J
Department of Biological Sciences, University of North Texas, Denton 76201.
Enzyme Protein. 1993;47(2):92-8. doi: 10.1159/000468662.
Extracts from the parenchymous leaf-gel of the Aloe vera plant (Aloe barbadensis Miller) were shown to contain glutathione peroxidase (GSHPx) activity. The activity was purified to homogeneity by ion exchange and gel filtration (FPLC) chromatography in the presence of 0.5 mM glutathione. The native enzyme has an apparent molecular weight of 62 kD as determined by gel filtration. In the presence of sodium dodecylsulfate (SDS), the molecular weight was estimated to be about 16 kD as determined by polyacrylamide-gel electrophoresis (SDS-PAGE). The native enzyme is proposed to be constituted of four identical subunits; it also contains one atom of selenium per subunit, as found with most glutathione peroxidases from animal sources. The Km values were determined to be 3.2 mM for glutathione and 0.26 mM for the hydroperoxide substrate, cumene hydroperoxide. The enzyme is competitively inhibited by N, S, bis-FMOC glutathione (Ki = 0.32 mM), a potent inhibitor of glyoxalase II. Inhibitors of glyoxalase I (e.g. S-octylglutathione) have no effect on the peroxidase activity.
已证明从库拉索芦荟（Aloe barbadensis Miller）的薄壁叶凝胶中提取的物质含有谷胱甘肽过氧化物酶（GSHPx）活性。在0.5 mM谷胱甘肽存在的情况下，通过离子交换和凝胶过滤（FPLC）色谱法将该活性纯化至同质。通过凝胶过滤测定，天然酶的表观分子量为62 kD。在十二烷基硫酸钠（SDS）存在的情况下，通过聚丙烯酰胺凝胶电泳（SDS-PAGE）测定，分子量估计约为16 kD。推测天然酶由四个相同的亚基组成；每个亚基还含有一个硒原子，这与大多数动物来源的谷胱甘肽过氧化物酶情况相同。谷胱甘肽的Km值测定为3.2 mM，氢过氧化物底物氢过氧化异丙苯的Km值为0.26 mM。该酶受到N，S，双-FMOC谷胱甘肽（Ki = 0.32 mM）的竞争性抑制，N，S，双-FMOC谷胱甘肽是乙二醛酶II的有效抑制剂。乙二醛酶I的抑制剂（例如S-辛基谷胱甘肽）对过氧化物酶活性没有影响。
