Protein disulphide isomerase

What is it? Protein disulphide isomerase is an enzyme with two interrelated activities: as an oxidoreductase, it can catalyse the formation, reduction and isomerisation of disulphide bonds; and as a polypeptide binding protein, it can function as a molecular chaperone which assists the folding of polypeptides. Transient association of PDI with nascent polypeptides during their folding prevents non-productive interactions from occurring, thereby increasing the yield of correctly folded protein molecules. PDI also forms more permanent associations with specific proteins, becoming a subunit of prolyl-4-hydroxylase or microsomal triglyceride transfer protein, depending on its partners.