Expression and characterization of Kluyveromyces lactis beta-galactosidase in Escherichia coli.
Kluyveromyces lactis beta-galactosidase gene, LAC4, was expressed in Escherichia coli as a soluble His-tagged recombinant enzyme under the optimized culture conditions. The expressed protein was multimeric with a subunit molecular mass of 118 kDa. The dimeric form of the beta-galactosidase was the major fraction but had a lower activity than those of the multimeric forms. The purified enzyme required Mn2+ for activity and was inactivated irreversibly by imidazole above 50 mM. The activity was optimal at 37 and 40 degrees C for o-nitrophenyl-beta-D-galactopyranoside (oNPG) and lactose, respectively. The optimum pH value is 7. The Km and Vmax values of the purified enzyme for oNPG were 1.5 mM and 560 micromol min(-1) mg(-1), and for lactose 20 mM and 570 micromol min(-1) mg(-1), respectively.
Kim
Chang Sup
CS
Department of Bioscience and Biotechnology, Sejong University, Seoul 143-747, South Korea.
Ji
Eun-Su
ES
Oh
Deok-Kun
DK
D003001:Cloning, Molecular / Q000379:methods*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D007716:Kluyveromyces / Q000201:enzymology* / Q000235:genetics*; D008970:Molecular Weight; D011522:Protons; D013696:Temperature; D001616:beta-Galactosidase / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics
D011522:Protons; D001616:beta-Galactosidase