Ghosh Shraboni, Majee Manoj
National Institute of Plant Genome Research, New Delhi, India.
National Institute of Plant Genome Research, New Delhi, India.
Vitam Horm. 2023;121:413-432. doi: 10.1016/bs.vh.2022.10.005. Epub 2022 Nov 29.
All life forms, including plants, accumulate reactive oxygen species (ROS) as a byproduct of metabolism; however, environmental stresses, including abiotic stresses and pathogen attacks, cause enhanced accumulation of ROS in plants. The increased accumulation of ROS often causes oxidative damage to cells. Organisms are able to maintain levels of ROS below permissible limits by several mechanisms, including efficient antioxidant systems. In addition to antioxidant systems, recent studies suggest that protein l-isoaspartyl methyltransferase (PIMT), a highly conserved protein repair enzyme across evolutionary diverse organisms, plays a critical role in maintaining ROS homeostasis by repairing isoaspartyl-mediated damage to antioxidants in plants. Under stress conditions, antioxidant proteins undergo spontaneous isoaspartyl (isoAsp) modification which is often detrimental to protein structure and function. This reduces the catalytic action of antioxidants and disturbs the ROS homeostasis of cells. This chapter focuses on PIMT and its interaction with antioxidants in plants, where PIMT constitutes a secondary level of protection by shielding a primary level of antioxidants from dysfunction and permitting them to guard during unfavorable situations.
所有生命形式，包括植物，都会积累活性氧（ROS）作为新陈代谢的副产物；然而，环境胁迫，包括非生物胁迫和病原体攻击，会导致植物体内ROS的积累增加。ROS积累的增加常常会对细胞造成氧化损伤。生物体能够通过多种机制，包括高效的抗氧化系统，将ROS水平维持在允许的限度以下。除了抗氧化系统外，最近的研究表明，蛋白质L-异天冬氨酰甲基转移酶（PIMT）是一种在进化上不同的生物体中高度保守的蛋白质修复酶，它通过修复植物中抗氧化剂的异天冬氨酰介导的损伤，在维持ROS稳态中起关键作用。在胁迫条件下，抗氧化蛋白会发生自发的异天冬氨酰（isoAsp）修饰，这通常对蛋白质的结构和功能有害。这会降低抗氧化剂的催化作用，并扰乱细胞的ROS稳态。本章重点介绍PIMT及其与植物中抗氧化剂的相互作用，其中PIMT通过保护一级抗氧化剂免于功能失调，并使其在不利情况下发挥保护作用，构成了二级保护水平。
