Characterization of a mutated Geobacillus stearothermophilus L-arabinose isomerase that increases the production rate of D-tagatose.
OBJECTIVE
Characterization of a mutated Geobacillus stearothermophilus L-arabinose isomerase used to increase the production rate of D-tagatose.


RESULTS
A mutated gene was obtained by an error-prone polymerase chain reaction using L-arabinose isomerase gene from G. stearothermophilus as a template and the gene was expressed in Escherichia coli. The expressed mutated L-arabinose isomerase exhibited the change of three amino acids (Met322-->Val, Ser393-->Thr, and Val408-->Ala), compared with the wild-type enzyme and was then purified to homogeneity. The mutated enzyme had a maximum galactose isomerization activity at pH 8.0, 65 degrees C, and 1.0 mM Co2+, while the wild-type enzyme had a maximum activity at pH 8.0, 60 degrees C, and 1.0-mM Mn2+. The mutated L-arabinose isomerase exhibited increases in D-galactose isomerization activity, optimum temperature, catalytic efficiency (kcat/Km) for D-galactose, and the production rate of D-tagatose from D-galactose.


CONCLUSIONS
The mutated L-arabinose isomerase from G. stearothermophilus is valuable for the commercial production of D-tagatose.


CONCLUSIONS
This work contributes knowledge on the characterization of a mutated L-arabinose isomerase, and allows an increased production rate for D-tagatose from D-galactose using the mutated enzyme.
Kim
H-J
HJ
Department of Bioscience and Biotechnology, Konkuk University, Seoul, Korea.
Kim
J-H
JH
Oh
H-J
HJ
Oh
D-K
DK
D019747:Aldose-Ketose Isomerases / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D019149:Bioreactors; D002412:Cations; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D001411:Geobacillus stearothermophilus / Q000235:genetics*; D006601:Hexoses / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology; D008969:Molecular Sequence Data; D009154:Mutation; D011994:Recombinant Proteins; D013549:Sweetening Agents; D013696:Temperature
D002412:Cations; D006601:Hexoses; D011994:Recombinant Proteins; D013549:Sweetening Agents; D019747:Aldose-Ketose Isomerases; C019714:D-arabinose isomerase; C030192:tagatose; D005690:Galactose