Protein disulfide isomerase (By similarity). Might play a role in the unfolded protein response (By similarity). May regulate transport of alpha4-beta2 neuronal acetylcholine receptor (PubMed:16238698). {ECO:0000250|UniProtKB:Q9CYA0, ECO:0000269|PubMed:16238698}. This is the function of CRELD2 (CRELD disulfide isomerase 2, ENSG00000184164).