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KMID : 0545120100200061018
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Journal of Microbiology and Biotechnology
2010 Volume.20 No. 6 p.1018 ~ p.1021
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Escherichia coli Arabinose Isomerase and Staphylococcus aureus Tagatose-6-Phosphate Isomerase: Which is a Better Template for Directed Evolution of Non-Natural Substrate Isomerization?
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Kim Hye-Jung
Uhm Tae-Guk
Kim Pil
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Abstract
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Two different categories of isomerization enzymes have been known: metallic isomerases and non-metallic isomerases. To understand better enzyme category for the directed evolution of L-arabinose isomerase from Escherichia coli (ECAI; EC 5.3.1.4) for a metallic isomerase and tagatose-6-phosphate isomerase from Staphylococcus aureus (SATI; EC 5.3.1.26) for a non-metallic isomerase were chosen as models. Random mutations were introduced into the genes of ECAI and SATI with same mutation rate and isomerization activities for non-natural substrate (galactose) were measured among the 515 samples of each mutated isomerases. With average mutation rate of 0.2 mutations/1kb, 47.5 % of the mutated ECAIs (270 out of 515 cases) showed increase of activity compared with wild-type ECAI while the rest ECAIs (52.5%; 243 out of 515 cases) showed decrease. In the same mutation rate, the mutated SATIs represent 58.6% increase and 41.4% decrease of activities. The maximum activity increase among 515 evolutions for ECAI was 130% and that for SATI was 190%. Based on the results, characteristics of the directed evolutions on the different isomerases were discussed for non-natural substrate isomerization.
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KEYWORD
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metallic arabinose isomerase, non-metallic tagatose-6-phosphate isomerase, directed evolution, evolutional comparison
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