Disulfide reductase which serves multiple functions in mitochondria, protecting mitochondrial components against thiol-oxidative damage as a thiol-disulfide oxidoreductase, and supporting urea cycle and respiration in mitochondria in a manner independent of active site thiols. Interacts with arg3. By aluminum chloride and ferrous chloride. Leads to auxotrophy for arginine and cysteine. Belongs to the thioredoxin family. Truncated N-terminus.