Overbaugh J M, Fall R
Department of Chemistry, and Cooperative Institute for Research in Environmental Sciences, Box 215, University of Colorado, Boulder, Colorado 80309.
Plant Physiol. 1985 Feb;77(2):437-42. doi: 10.1104/pp.77.2.437.
Light or dark grown Euglena gracilis strains contain similar levels of glutathione (GSH) peroxidase. Cells in midstationary phase of growth contained the highest level of the enzyme. The enzyme was purified 280-fold to homogeneity from the permanently bleached strain, E. gracilis var bacillaris W(3)BUL. The native enzyme has a molecular weight of 130,000 as measured by gel permeation chromatography, and contains four subunits (mol wt 31,500) as measured by sodium dodecyl sulfate gel electrophoresis. A variable amount of a higher molecular weight form of the enzyme (approximate mol wt 250,000) was detected but not further characterized. The enzyme has an isoelectric point of 4.7. No selenium could be detected in the purified enzyme. The enzyme is active with H(2)O(2) and a variety of organic hydroperoxides, including 13-hydroperoxylinoleic acid, and is specific for GSH as the thiol substrate. Apparent K(m) values for H(2)O(2), t-butyl hydroperoxide, and GSH were 0.03, 1.5, and 0.7 millimolar, respectively. A comparison of selenium-dependent and selenium-independent GSH peroxidases from various eukaryotic sources is presented.
光照或黑暗条件下生长的纤细裸藻菌株所含谷胱甘肽（GSH）过氧化物酶水平相似。处于生长中期稳定期的细胞中该酶水平最高。从永久漂白菌株纤细裸藻巴氏变种W(3)BUL中纯化该酶280倍至均一状态。通过凝胶渗透色谱法测得天然酶分子量为130,000，通过十二烷基硫酸钠凝胶电泳测得其含有四个亚基（分子量31,500）。检测到该酶存在可变数量的较高分子量形式（约250,000），但未进一步鉴定。该酶的等电点为4.7。纯化后的酶中未检测到硒。该酶对H₂O₂和多种有机氢过氧化物有活性，包括13-氢过氧亚油酸，并且对作为硫醇底物的GSH具有特异性。H₂O₂、叔丁基氢过氧化物和GSH的表观K(m)值分别为0.03、1.5和0.7毫摩尔。本文对来自各种真核生物来源的硒依赖性和非硒依赖性GSH过氧化物酶进行了比较。
