Protein Disulfide Isomerase A5 (PDIA5)

Protein Disulfide Isomerase A5is an enzyme in the endoplasmic reticulum in eukaryotes or periplasmic space of prokaryotes that catalyzes the formation and breakage of disulfide bonds between cysteine residues within proteins as they fold. This allows proteins to quickly find the correct arrangement of disulfide bonds in their fully-folded state, and therefore the enzyme acts to catalyze protein folding.

In the chloroplasts of the unicellular algae Chlamydomonas reinhardtii the PDI RB60 serves as a redox sensor component of an mRNA binding protein complex implicated in the photo-regulation of the translation of psbA, the RNA encoding for the photoisystem II core protein D1. PDI has also been suggested to play a role in the formation of regulatory disulfide bonds in chloroplasts