Partial purification and characterization of transglutaminase from threadfin bream (Nemipterus sp.) liver

Transglutaminase (TGase) from the threadfin bream ([TB] Nemipterus sp.) liver was partially purified using ion exchange, size exclusion and affinity chromatography. Three protein bands with molecular weight (Mw) of 95, 63 and 43 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were observed. Only one distinct fluorescent band appeared on the TGase activity staining of the native-PAGE. When the protein band was eluted and analyzed on the SDS-PAGE, it showed a single band with an Mw of 95 kDa. The enzyme required Ca2+ up to 1 mM for full activation. TGase was also activated by 10 mM Sr2+. Dithiothreitol had no effect on activity. TGase activity was unaffected by NaCl up to 0.6 M and reduced to 75% at 1.2 M NaCl. Optimum pH and temperature was 8.5-9.0 and 50C, respectively. TGase activity was markedly inhibited by the sulfhydryl reagents. The enzyme catalyzed the cross-linking of the TB myosin heavy chains.