Improvement of tagatose conversion rate by genetic evolution of thermostable galactose isomerase.
To enhance the isomerization rate of galactose into tagatose, a thermostable galactose isomerase, which was isolated from bacteria growing in a hot spring, was genetically improved using the error-prone PCR method. From 500 mutant clones, a clone showing improved conversion activity was selected. The sequence of the selected clone had five amino acid changes: His(228)-->Asp, Gly(384)-->Asp, Ser(393)-->Thr, Lys(428)-->Asn and Asp(475)-->Lys. The improved galactose isomerase had an 11-fold higher reaction rate than the original.
Kim
P
P
R & D Center, Tongyang Confectionery Co., 30-10 Munbai-dong, Yongsan-ku, Seoul 140-715, Korea. kpil718@hanmail.net
Yoon
S H
SH
Seo
M J
MJ
Oh
D K
DK
Choi
J H
JH
D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence / Q000235:genetics; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004795:Enzyme Stability / Q000235:genetics; D005690:Galactose / Q000378:metabolism*; D006601:Hexoses / Q000378:metabolism*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D015202:Protein Engineering / Q000379:methods
D001426:Bacterial Proteins; D006601:Hexoses; D019747:Aldose-Ketose Isomerases; C019715:L-arabinose isomerase; C030192:tagatose; D005690:Galactose