Characterization of an l-arabinose isomerase from the Lactobacillus plantarum NC8 strain showing pronounced stability at acidic pH.
Gene araA encoding the l-arabinose isomerase (l-AI) from Lactobacillus plantarum NC8 was cloned and expressed in Escherichia coli. It encodes a polypeptide of 474 residues having 55% identities with l-AIs from Bacillus stearothermophilus US100 and Thermus sp. IM6501. The active form of the purified recombinant l-AI NC8 enzyme is a hexamer composed of six identical 55-kDa subunits. The purified enzyme was optimally active at 60 degrees C and pH 7.5. It required divalent cations such as Co(2+) and Mn(2+) for maximal activity and thermostability. The l-AI NC8 was exceptionally active and stable at acidic pH. Indeed, it exhibited 68% of its maximal activity at pH 5.5 and retained 89% of activity after a 24-h incubation at pH 5. The apparent K(m) values of the enzyme for l-arabinose and d-galactose were 43.4 and 69.7 mM, respectively, and its catalytic efficiency was c. 10-fold higher for the physiological substrate l-arabinose (15.5 mM(-1) min(-1)) than d-galactose (1.6 mM(-1) min(-1)). The bioconversion yield of d-galactose to d-tagatose by the purified l-AI NC8 after 6 h at 60 degrees C was 30%.
Chouayekh
Hichem
H
Bejar
Wacim
W
Rhimi
Moez
M
Jelleli
Karim
K
Mseddi
Malek
M
Bejar
Samir
S
D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000235:genetics*; D001089:Arabinose / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics*; D002413:Cations, Divalent / Q000378:metabolism; D003001:Cloning, Molecular; D003067:Coenzymes / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D005690:Galactose / Q000378:metabolism; D015870:Gene Expression; D006601:Hexoses / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D048191:Lactiplantibacillus plantarum / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D013696:Temperature
D001426:Bacterial Proteins; D002413:Cations, Divalent; D003067:Coenzymes; D004269:DNA, Bacterial; D006601:Hexoses; D011994:Recombinant Proteins; D001089:Arabinose; D019747:Aldose-Ketose Isomerases; C019715:L-arabinose isomerase; C030192:tagatose; D005690:Galactose