Proteins are essential molecules that carry out key functions in a cell. However, as a result of aging or stressful environments, the protein undergoes a range of spontaneous covalent modifications, including the formation of abnormal l-isoaspartyl residues from aspartyl or asparaginyl residues, which can disrupt the protein's inherent structure and function. PROTEIN l-ISOASPARTYL METHYLTRANSFERASE (PIMT: EC 2.1.1.77), an evolutionarily conserved ancient protein repairing enzyme (PRE), converts such abnormal l-isoaspartyl residues to normal l-aspartyl residues and re-establishes the protein's native structure and function. Although originally discovered in animals as a PRE, PIMT emerged as a key PRE in plants, particularly in seeds, in which PIMT plays a predominant role in preserving seed vigor and viability for prolonged periods of time. Interestingly, higher plants encode a second PIMT (PIMT2) protein which possesses a unique N-terminal extension, and exhibits several distinct features and far more complexity than non-plant PIMTs. Recent studies indicate that the role of PIMT is not restricted to preserving seed vigor and longevity but is also implicated in enhancing the growth and survivability of plants under stressful environments. Furthermore, expression studies indicate the tantalizing possibility that PIMT is involved in various physiological processes apart from its role in seed vigor, longevity and plant's survivability under abiotic stress. This review article particularly describes new insights and emerging interest in all facets of this enzyme in plants along with a concise comparative overview on isoAsp formation, and the role and regulation of PIMTs across evolutionary diverse species. Additionally, recent methods and their challenges in identifying isoaspartyl containing proteins (PIMT substrates) are highlighted.

中文翻译：

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植物中的蛋白质1-异戊烯基甲基转移酶（PIMT）：法规和功能

蛋白质是在细胞中执行关键功能的必需分子。然而，由于衰老或压力环境，蛋白质会经历一系列自发的共价修饰，包括由天冬氨酰或天冬酰胺基残基形成异常的1-异天冬氨酰残基，这会破坏蛋白质的固有结构和功能。蛋白质1-异戊烯基甲基转移酶（PIMT：EC 2.1.1.77）是一种进化保守的古代蛋白质修复酶（PRE），可将此类异常的1-异天冬氨酰残基转化为正常的1-天冬氨酰残基，并重新建立蛋白质的天然结构和功能。尽管PIMT最初在动物中以PRE的形式发现，但PIMT却已成为植物（尤其是种子）中的关键PRE，其中PIMT在长时间保持种子活力和生存力中起主要作用。有趣的是，高等植物编码第二个PIMT（PIMT2）蛋白，该蛋白具有独特的N端延伸，并且比非植物PIMT表现出几个独特的特征并且复杂得多。最近的研究表明，PIMT的作用不仅限于保持种子活力和寿命，而且还涉及在胁迫环境下增强植物的生长和存活性。此外，表达研究表明，PIMT除了在非生物胁迫下对种子活力，寿命和植物生存能力的作用外，还参与了各种生理过程。这篇评论文章特别介绍了这种酶在植物各个方面的新见识和新兴趣，以及对isoAsp形成的简要比较概述，以及PIMT在进化多样性物种中的作用和调控。另外，突出了鉴定含异天冬氨酰的蛋白质（PIMT底物）的最新方法及其挑战。