TXNDC12 belongs to the thioredoxin superfamily. Members of this superfamily possess a thioredoxin fold with a consensus active-site sequence (CxxC) and have roles in redox regulation, defense against oxidative stress, refolding of disulfide-containing proteins, and regulation of transcription factors.The deduced 172-amino acid protein has a calculated molecular mass of 19.2 kD. TLP19 has an N-terminal signal peptide and a central thioredoxin-like domain containing the consensus active-site motif. Northern blot analysis detected a 1.6-kb TLP19 transcript in all tissues examined, with highest expression in placenta and liver. Placenta also expressed a 1.2-kb TLP19 transcript. Epitope-tagged TLP19 was expressed in the Golgi apparatus of transiently transfected COS-7 cells, and it was secreted into the culture medium.