Enables protein-disulfide reductase activity. Acts upstream of or within cell redox homeostasis; negative regulation of protein export from nucleus; and negative regulation of transcription by RNA polymerase II. Located in cytosol and nucleus. Is expressed in central nervous system; skeleton; and submandibular gland primordium. Orthologous to human TXN (thioredoxin). [provided by Alliance of Genome Resources, Apr 2022]