SummaryTissue transglutaminase was reported to act as protein disulfide isomerase (PDI). We studied whether plasma transglutaminase – coagulation factor XIII (FXIII) – has PDI activity as well. PDI activity was measured by determining the ability to renature reduced-denatured RNase (rdRNase). We found that FXIII can re-nature rdRNase, with efficiency comparable to commercial PDI. This PDI activity was inhibited by bacitracin. Like tissue transglu-taminase, FXIII-mediated PDI activity is independent of its transglutaminase activity and is located on the A subunit. Surface-associated PDI has been previously shown to catalyse two distinct functions: transnitrosation with subsequent release of intracellular nitric oxide and disulfide bond rearrangement during platelet integrin ligation. Our results imply that FXIII-PDI activity may have a role in platelet function.
Factor XIII improves platelet adhesion to fibrinogen by protein disulfide isomerase-mediated activity
