Yanik Tulin, Donaldson Robert Paul
Department of Biological Sciences, The George Washington University, Lisner Hall, 2023 G St. NW #340, Washington, DC 20052, USA.
Arch Biochem Biophys. 2005 Mar 15;435(2):243-52. doi: 10.1016/j.abb.2004.12.017.
Glyoxysomes are specialized peroxisomes in germinating seeds, which catalyze many reactions that convert fatty acids into carbohydrates thus generating H(2)O(2). They are characterized by the presence of catalase (CAT, E.C. 1.11.1.6) in their matrix which protects cells from oxidative stress. Here, we investigated the possibility that a protein can be protected from oxidative damage by its association with CAT. We purified peroxisomal CAT from germinating castor beans by ion exchange, gel filtration, and hydroxylapatite chromatography. Gel filtration of the matrix proteins, cross-linking, and co-immunoprecipitation studies indicate that CAT associates with a glyoxysomal matrix protein, isocitrate lyase (ICL, E.C. 4.1.3.1). In addition, we found that H(2)O(2) inactivates ICL and degrades its product, glyoxylate, when CAT is inactive. ICL and its product appear to be sensitive to oxidative damage; thus, association of CAT with ICL would afford protection from H(2)O(2).
乙醛酸循环体是萌发种子中的特殊过氧化物酶体，它催化许多将脂肪酸转化为碳水化合物的反应，从而产生过氧化氢。其特征是在基质中存在过氧化氢酶（CAT，E.C. 1.11.1.6），该酶可保护细胞免受氧化应激。在此，我们研究了一种蛋白质通过与CAT结合而免受氧化损伤的可能性。我们通过离子交换、凝胶过滤和羟基磷灰石色谱法从萌发的蓖麻籽中纯化了过氧化物酶体CAT。对基质蛋白进行凝胶过滤、交联和共免疫沉淀研究表明，CAT与乙醛酸循环体基质蛋白异柠檬酸裂解酶（ICL，E.C. 4.1.3.1）结合。此外，我们发现当CAT无活性时，过氧化氢会使ICL失活并降解其产物乙醛酸。ICL及其产物似乎对氧化损伤敏感；因此，CAT与ICL的结合可提供对过氧化氢的保护。
