Purification And Properties Of Transglutaminase From Maize Leaves

Transglutaminase (TGase) is an enzyme which can catalyze the transfer reactions of acyl. TGase distributes widely in tissues of plants and animals and microorganisms. TGase from animals is scarce, and the purification is complex and depends on Ca2+, thus it's difficult to get a large-scale application. At present, microorganism TGase is widely applied. However, the reports on TGase from maize are few. In the present study, a kind of TGase from maize leaves is partly purified. Its properties are investigated, in which the effets of temperature and pH on its activity involved. Then, the application properties of the partly purified TGase in yoghurt were determined. According to the comparison with the properties of microbiological TGase, the potential application of TGase from maize is evaluated.During the purification process, the parameters of centrifugation, ultrafiltration and gel filtration chromatography were optimized. TGase from maize leaves was partly purified by the optimized conditions, the specific activity of enzyme was 27.28 U/g.pro and the recovery rate was 13.84%. It identified the molecular weight of maize TGase is 61 kDa, and the purity was 3.0%.With purified maize TGase as sample, it studied the two most important factors as temperature and pH which affect the enzyme activity greatly. It showed the optimum temperature was 35℃for maize TGase where it had the best stability of enzymatic activity. In the range of 30 ~ 45℃, the optimum pH was 9.0 for maize TGase and the best stability of enzymatic activity was pH 8.0. It had better enzymatic activity from pH 8.0 to pH 9.0. By differential scanning calorimetry, it found that the initial temperature of the enzyme protein denaturation was 46.03℃and the phase transition temperature was 60.50℃.By adding microbial TGase and maize TGase into the full cream yoghurt before inoculation, it showed yoghourts treated with TGase had a higher hardness and consistency than untreated samples. While, the yoghurt with maize TGase had the lowest viscosity and viscous index. From the appearance, the yogurts with TGase had some obvious granular precipitation.Comprehensive results of this study show that maize TGase is better than microbial TGase in temperature stability, but inferiorer to microbial TGase in pH stability. Therefore, maize TGase can be used in some food with more stringent temperature requirements, but has some limitations of applications in some food with lower pH. Therefore, as a catalyzer of having some proteins cross-linking, it has a certain potential in industiral application.