Enables protein-disulfide reductase activity. Involved in determination of adult lifespan. Located in several cellular components, including neuronal cell body; nucleus; and plasma membrane bounded cell projection. Expressed in ASJL; ASJR; and head neurons. Human ortholog(s) of this gene implicated in cardiomyopathy (multiple); coronary artery disease (multiple); and male infertility. Is an ortholog of human TXN (thioredoxin).