Large-size subunit catalases (LSCs) have a C-terminal domain that is structurally similar to DJ-1 and Hsp31 proteins, which have well documented molecular chaperone activity. Like chaperones, LSCs are abundant proteins that are induced under stress conditions and during cell differentiation in different microorganisms. Here we document that the C-terminal domain of LSCs assist other proteins to preserve their active conformation. Heat, urea, or H₂O₂ denaturation of alcohol dehydrogenase was prevented by LSCs or the C-terminal domain of Catalase-3 (TDC3); in contrast, small-size subunit catalases (SSCs) or LSCs without the C-terminal domain (C3^ΔTD or C63) did not have this effect. Similar results were obtained if the alcohol dehydrogenase was previously denatured by heat and then the different catalases or truncated enzymes were added. The TDC3 also protected both the C3^ΔTD and the bovine liver catalase from heat denaturation. The chaperone activity of CAT-3 or the TDC3 increased survival of E. coli under different stress conditions whereas the C3^ΔTD did not. It is concluded that the C-terminal domain of LSCs has a chaperone activity that is instrumental for cellular resistance to stress conditions, such as oxidative stress that leads to cell differentiation in filamentous fungi.

大型亚基过氧化氢酶（LSC）的C末端结构域与DJ-1和Hsp31蛋白在结构上相似，后者具有充分记录的分子伴侣活性。像伴侣蛋白一样，LSC是在应激条件下以及在不同微生物的细胞分化过程中诱导的丰富蛋白质。在这里，我们证明LSC的C末端结构域有助于其他蛋白质保留其活性构象。LSC或过氧化氢酶3（TDC3）的C端结构域阻止了醇脱氢酶的热，尿素或H ₂ O ₂变性；相反，没有C末端结构域的小型亚单位过氧化氢酶（SSC）或LSC（^C3ΔTD或C63）没有此效果。如果事先通过加热使乙醇脱氢酶变性，然后加入不同的过氧化氢酶或截短的酶，则可获得相似的结果。TDC3还保护^C3ΔTD和牛肝过氧化氢^酶免受热变性。CAT-3或TDC3的分子伴侣活性提高了大肠杆菌在不同胁迫条件下的存活率，而^C3ΔTD却没有。结论是，LSC的C-末端结构域具有分子伴侣活性，该分子伴侣活性对于细胞对应激条件的抗性是重要的，例如氧化应激导致丝状真菌中的细胞分化。