Abstract
Transglutaminase (TGase) is widely used in the food industry. In this study, TGase was purified by affinity precipitation using l-thyroxin, coupled to a thermo-responsive polymer (PNBN), as an affinity ligand. The lower critical solution temperature and recovery of the affinity polymer were 31.0 °C and 99.6 %, respectively. The optimal adsorption condition was 0.02 mol/L phosphate buffer (pH 5.0). The recoveries 99.01 % (protein) and 98.85 % (activity) were obtained by 0.2 mol/L Gly–NaOH buffer (pH 10.0) as the elution agent. Circular dichroism spectroscopy and FortéBio Octet system were used to explore the interactions between l-thyroxin and TGase. The results show that l-thyroxin is suitable for affinity precipitation of TGase. The purity of the final product was verified using sodium dodecyl sulfate polyacrylamide gel electrophoresis.
Highlights
Transglutaminase (TGase; EC 2.3.2.13) is an enzyme that can catalyze the acyl-transfer reaction from the γ-carboxamide group of a glutamine residue to the ε-amino group of a lysine residue (Grossowicz et al 1950; Folk 1980)
The circular dichroism (CD) spectrum of TGase had a negative band in the UV region near 220 nm, which is characteristic of an α-helical structure, and the α-helix ratio in the secondary structure of TGase decreased from
31.98 % (a) to 28.26 % (b), 25.45 % (c) or 21.08 % (d) as in Fig. 2 by adding different concentrations of l-thyroxin. These results indicate that the ligand underwent interactions with TGase, and that increasing the amount of l-thyroxin caused greater changes in the secondary structure of TGase
Summary
Transglutaminase (TGase; EC 2.3.2.13) is an enzyme that can catalyze the acyl-transfer reaction from the γ-carboxamide group of a glutamine residue to the ε-amino group of a lysine residue (Grossowicz et al 1950; Folk 1980). When water molecules act as the acyl receptor, the deamidation of the glutamine and formation of a glutamine acid occur (Pardin et al 2009). This enzyme has a wide range of applications in food, drugs, immune studies, and metabolism (Binsi and Shamasundar 2012). Proteins play an important role in the nutritional values and composition of most foods, and TGase can cross-link many important food proteins such as casein and soy proteins. These modifications by TGase affect the solubility, gelation, emulsification, and other
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