Abstract

Transglutaminase from its zymogen, blood coagulation Factor XIII, catalyzes the covalent intermolecular polymerization of fibrin through formation of ε (γ-glutamyl) lysine crosslink. In recent years, considerable progress has been made in understanding the molecular and catalytic Properties of Factor XIII. However, the metabolic aspects of Factor XIII under various physiological conditions are not fully understood. Lee and Chung (1976) elucidated that plasma protransglutaminase is synthesized in hepatocytes. In this report we observed the mode of synthesis and the secretion of plasma pro-transglutaminase in vivo. Rabbits were used as the experimental model. The results were as follows : 1. Both a and b-chains incorporated by [75Se] -L-methionine in the liver showed their maximum values at 30 minutes after [75Se] -L-methionine infusion, then the values continued to decrease up to 2 hours, followed by plateau of 4 hours, whereas those in the plasma rapid1y increased up to 3 hours, and then showed a plateau. Plasma fibrinogen showed the same pattern as that of plasma protransglutaminase. 2. B-chains were formed and secreted at a much larger rate than a-chains. 3. Protransglutaminase was formed and secreted at a much larger rate than fibrinogen.