Probably required during the final stages of sperm tail maturation in the testis and/or epididymis, where extensive disulfide bonding of fibrous sheath (FS) proteins occurs. In vitro, it has neither nucleoside diphosphate kinase (NDPK) activity nor reducing activity on disulfide bonds (PubMed:11737268). Exhibits a 3′-5′ exonuclease activity with a preference for single-stranded DNA, suggesting roles in DNA proofreading and repair (PubMed:16313181).
