PO4DB, or Prolyl 4-hydroxylase, beta polypeptide, is a human gene encoded by P4HB. It may also be known as: Protein disulfide-isomerase; PDI; Cellular thyroid hormone-binding protein; Prolyl 4-hydroxylase subunit beta; protein disulfide isomerase-associated 1; protein disulfide isomerase family A, member 1; collagen prolyl 4-hydroxylase beta; DSI; ERBA2L; GIT; P4Hbeta; PDIA1; PHDB; PO4HB; PROHB. The encoded protein is an enzyme with an amino acid length of 508 and a mass of 57.1 kDa. Other isoforms may exist. PO4DB is a member of the Protein disulfide isomerase family. Homologs of this gene exist in other organisms, including: Fly, Arabidopsis, Nematode.