Proteins are the principal biomolecules in bacteria that are affected by the oxidants produced by the phagocytic cells. Most of the protein damage is irreparable though few unfolded proteins and covalently modified amino acids can be repaired by chaperones and repair enzymes respectively. This study reviews the three protein repair enzymes, protein l-isoaspartyl O-methyl transferase (PIMT), peptidyl proline cis-trans isomerase (PPIase), and methionine sulfoxide reductase (MSR). Published articles regarding protein repair enzymes were collected from Google Scholar and PubMed. The information obtained from the research articles was analyzed and categorized into general information about the enzyme, mechanism of action, and role played by the enzymes in bacteria. Special emphasis was given to the importance of these enzymes in Salmonella Typhimurium. Protein repair is the direct and energetically preferred way of replenishing the cellular protein pool without translational synthesis. Under the oxidative stress mounted by the host during the infection, protein repair becomes very crucial for the survival of the bacterial pathogens. Only a few covalent modifications of amino acids are reversible by the protein repair enzymes, and they are highly specific in activity. Deletion mutants of these enzymes in different bacteria revealed their importance in the virulence and oxidative stress survival. PIMT repairs isoaspartate residues, PPiase catalyzes the conversion of cis-trans forms of proline residues, while MSR repairs oxidized methionine (Met) residues in the proteins. These repair enzymes maintain the activities of the target protein(s), thus aid in bacterial survival and virulence. The interventions which can interfere with this mechanism could be used for the development of novel therapeutics.

中文翻译：

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蛋白质修复酶在沙门氏菌氧化应激存活和毒力中的作用

蛋白质是细菌中的主要生物分子，受吞噬细胞产生的氧化剂影响。大多数蛋白质损伤是无法弥补的，尽管很少的未折叠蛋白和共价修饰的氨基酸可以分别被伴侣蛋白和修复酶修复。这项研究审查了三种蛋白质修复酶，蛋白质l-异天冬氨酰O-甲基转移酶（PIMT），肽基脯氨酸顺反异构酶（PPIase）和蛋氨酸亚砜还原酶（MSR）。有关蛋白质修复酶的已发表文章收集自Google Scholar和PubMed。分析从研究文章中获得的信息，并将其归类为有关酶，作用机理以及酶在细菌中所起的作用的一般信息。特别强调了这些酶在鼠伤寒沙门氏菌中的重要性。蛋白质修复是在不进行翻译合成的情况下补充细胞蛋白质库的直接且在能量上优选的方式。在宿主在感染过程中产生的氧化应激下，蛋白质修复对于细菌性病原体的生存至关重要。蛋白质修复酶只能逆转氨基酸的少数共价修饰，并且它们的活性高度特异性。这些酶在不同细菌中的缺失突变体显示出它们在毒力和氧化应激存活中的重要性。PIMT修复异天冬氨酸残基，PPiase催化脯氨酸残基的顺式反式转化，而MSR修复蛋白质中的氧化蛋氨酸（Met）残基。这些修复酶维持靶蛋白的活性，因此有助于细菌存活和毒力。