Rational design of a disulfide bridge increases the thermostability of microbial transglutaminase

Microbial transglutaminase (MTG) has numerous industrial applications in the food and pharmaceutical sectors. Unfortunately, the thermostability of MTG is too low to tolerate the desired conditions used in many of these commercial processes. In a previous study, we used protein engineering to improve the thermostability of MTG. Specifically, we generated a T7C/E58C mutant of MTG from Streptomyces mobaraensis that displayed enhanced resistance to thermal inactivation. In this study, a rational structure-based approach was adopted to introduce a disulfide bridge to further increase the thermostability of MTG. In all, four new mutants, each containing a novel disulfide bond, were engineered. Of these four mutants, D3C/G283C showed the most promising thermostability with a significantly higher AT 50 (defined as the temperature of incubation at which 50% of the initial activity remains) of + 9 degrees C by comparison to wild-type MTG. Indeed, D3C/G283C combined enhanced thermostability with a 2.1-fold increased half-life at 65 degrees C compared with the wild-type enzyme. By structure-based rational design, we were able to create an MTG variant which might be useful for expanding the scope of application in food.

Automated summary

This study successfully improved the thermostability of microbial transglutaminase (MTG) through protein engineering and a structure-based approach. The most promising mutant, D3C/G283C, exhibited higher activity and longer half-life at high temperatures, which may expand its application in the food industry.