Study On Characterization Of Transglutaminase From Streptoverticillium SK4.001 And Its Application In Bread

Transglutaminase (TGase) is a kind of thiol enzyme that catalyzes acryl-transfer reaction, which introduces inter- or intra-molecular covalent crosslinks in many proteins, changing the quality of food products. TGase has been widely used in food industry. In this study, TGase from Streptoverticillium SK4.001 was intensively investigated.TGase from Streptoverticillium SK4.001 was purified by ion-exchange chromatography with Fractogel EMD SO₃^- and gel filtration chromatography with Superdex 75 (10/300GL). The purified enzyme gave a single band on SDS-polyacrylamide gel electrophoresis. The molecular masses of the enzyme was determined to be 40.4 kDa by SDS-PAGE and gel filtration chromatography.The purified TGase exhibited optimum activity at 50℃and pH 7.0. It was stable at 20-40℃and within a pH range of 5.6–7.0. The enzyme was not inhibited by Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, but it was strongly inactivated by Zn²⁺, Fe³⁺, Cu²⁺, Pb²⁺ and was partly inhibited by Mn²⁺,suggesting that this enzyme could not possess a metal ion at the active site. The purified enzyme presented a Km of 15.81 mM and a Vmax of 16.69 U/mL for CBZ-Gln-Gly. The N-terminal amino acid sequence of TGase was found to be DSDERVTPPAEPLDR.In an appropriate added amount, TGase can improve the farinograph characteristics and extensigraph characteristics of dough. Moreover, TGase not only markedly improved the quality of baking and the baked bread, it also led to an increase in the volume and specific volume of bread. It could improve the texture of crumb as well as significantly reduce retrogradation and staling during the storage period. In generally speaking, the optimal addition was 1500U/kg flour.Using scanning electron microscopy (SEM),it was found that the gluten continuous phase of treated dough appeared more tight and uniform than untreated dough. TGase could introduce covalent crosslinks in proteins to improve gluten network. TGase treatment resulted in a substantial increase in storage modulus values of hydrated gulten, which appeared to be not only less frequency dependent but also less temperature dependent.