원문정보
초록
영어
The S213C, I33L, and I33L-S213C mutant psicose 3-epimerases from Agrobacterium tumefaciens, which were obtained by random and site-directed mutagenesis, had 0, 5, and 10 °C increases in optimal temperature, 3.3-, 7.2-, and 29.9-fold increases in half-life at 50 °C, and 3.1, 4.3, and 7.6 °C increases in melting temperature, respectively, compared with the wild-type enzyme. Molecular modeling suggests that the improvement of thermostability was due to the formation of new aromatic stacking interaction in the I33L mutant enzyme and the increases of putative hydrogen bonds in the S213C mutant enzyme. The activity of the immobilized wild-type enzyme was decreased after 9 days with borate and 17 days without borate in a packed-bed bioreactor, but the activity of the immobilized double-site mutant enzyme was not decreased during the operation time of 30 days. These results suggest that the double-site mutant enzyme will be useful as an industrial producer of D-psicose.