Yang T, Poovaiah B W
Laboratory of Plant Molecular Biology and Physiology, Department of Horticulture, Washington State University, Pullman, WA 99164-6414, USA.
Proc Natl Acad Sci U S A. 2002 Mar 19;99(6):4097-102. doi: 10.1073/pnas.052564899. Epub 2002 Mar 12.
Environmental stimuli such as UV, pathogen attack, and gravity can induce rapid changes in hydrogen peroxide (H(2)O(2)) levels, leading to a variety of physiological responses in plants. Catalase, which is involved in the degradation of H(2)O(2) into water and oxygen, is the major H(2)O(2)-scavenging enzyme in all aerobic organisms. A close interaction exists between intracellular H(2)O(2) and cytosolic calcium in response to biotic and abiotic stresses. Studies indicate that an increase in cytosolic calcium boosts the generation of H(2)O(2). Here we report that calmodulin (CaM), a ubiquitous calcium-binding protein, binds to and activates some plant catalases in the presence of calcium, but calcium/CaM does not have any effect on bacterial, fungal, bovine, or human catalase. These results document that calcium/CaM can down-regulate H(2)O(2) levels in plants by stimulating the catalytic activity of plant catalase. Furthermore, these results provide evidence indicating that calcium has dual functions in regulating H(2)O(2) homeostasis, which in turn influences redox signaling in response to environmental signals in plants.
紫外线、病原体侵袭和重力等环境刺激可诱导植物体内过氧化氢（H₂O₂）水平迅速变化，从而引发多种生理反应。过氧化氢酶参与将H₂O₂降解为水和氧气的过程，是所有需氧生物中主要的H₂O₂清除酶。在应对生物和非生物胁迫时，细胞内的H₂O₂与胞质钙之间存在密切的相互作用。研究表明，胞质钙的增加会促进H₂O₂的生成。在此我们报告，钙调蛋白（CaM）是一种普遍存在的钙结合蛋白，在有钙存在的情况下，它能与一些植物过氧化氢酶结合并激活这些酶，但钙/CaM对细菌、真菌、牛或人的过氧化氢酶没有任何影响。这些结果证明，钙/CaM可通过刺激植物过氧化氢酶的催化活性来下调植物体内的H₂O₂水平。此外，这些结果提供了证据，表明钙在调节H₂O₂稳态方面具有双重功能，而H₂O₂稳态又反过来影响植物对环境信号的氧化还原信号传导。
