Transglutaminase activity in pancreatic islets

Abstract

1. Pancreatic islet homogenates catalyze, in a Ca 2+-dependent fashion, the incorporation of [2,5- 3H]histamine, [1,4- 14C]putrescine, [1,2- 3H]agmatine, [ 14C]methylamine, L-[U- 14C]lysine in N, N-dimethylcasein. 2. Using [2,5- 3H]histamine as the amine donor, the K m for Ca 2+ and histamine amounts to 90μM and 0.7 mM, respectively. 3. The incorporation of [2,5- 3H]histamine into N, N-dimethylcasein is inhibited by monodansylcadaverine, N- p-tosyl glycine, bacitracin and methylamine, the relative extent of inhibition depending on the respective concentrations of Ca 2+, inhibitor and amine donor. 4. Bacitracin and methylamine, but not N- p-tosyl glycine, cause a dose-related inhibition of glucose-stimulated insulin release. 5. It is concluded that, in pancreatic islets, the Ca 2+-responsive transglutaminase activity plays a critical role in the process of glucose-induced insulin release.