Chemical Modification of Transglutaminase for Improving Specific Activity and Thermal Stability

Abstract:

Transglutaminase（EC 2.3.2.13，TGase） can catalyze the acyl transfer reaction and leads to the crosslinking among proteins. It has been widely used in food，textile，leather，and pharmaceutical industry. In order to improve the specific activity and thermal stability，a recombinant Streptomyces hygroscopicus TGase chemically was modified by phthalic anhydride（PA） in this study. The optimal modification condition of the cultivation was at pH 8.0，20 ℃ for 2 h，and the molar ratio of surface-amine to phthalic anhydride 1∶2. In the presence of 10 mmol/L of cystamine，which is a competitive inhibitor of the TGase，the thermal stability of TGase was increased 31.3% after the PA modification，whereas specific activity of the TGase increased 48.3% in the absence of the cystamine. The modeling crystal structure showed that 21 lysine residues existed in surface of S. hygroscopicus TGase，and five of them located at region close the active site. The analysis of surface hydrophobicity indicated that PA modification reduced the surface hydrophobicity from 9.46% to 21.13%. Thus，PA may improve the specific activity and thermal stability of TGase by modifying the surface hydrophobicity at different regions. These results suggested that PA modification was an effective way to improve the catalytic properties of TGase，which provided a theoretical reference for molecular modification.