Role of astakinel in regulating transglutarninase activity

Transglutaminase (TGase) has been implicated in maintaining the undifferentiated stage of hematopoietic stem cells (HSC) in the crayfish Pacifastacus leniusculus. TGase activity has been reported to be regulated by astakinel, an essential crayfish cytokine for inducing new hemocyte synthesis in hematopoietic tissue (HPT). Here, the role of astakinel in TGase activity regulation and clotting protein (CP) cross-linking was characterized. A reduction in TGase activity was observed by the addition of purified astakinel in vitro for both endogenous crayfish TGase and a commercial purified guinea pig liver TGase. As a result, we observed that astakinel inhibits TGase enzyme activity and acts as a non-competitive inhibitor for the TGase enzyme. Additionally, the clotting reaction was impaired in the presence of astakinel. A decrease in TGase-mediated crosslinking of epsilon(gamma-glutamyl)-lysine bonds was also observed in the presence of astakinel. In conclusion, this study shows that astakinel acts as an inhibitor of TGase activity and that it also affects CP cross-linking during crayfish hematopoiesis. (C) 2017 Elsevier Ltd. All rights reserved.