The glucose dehydrogenase gene (gdh), cloned from Bacillus sp. G3, was composed of 786 bp nucleotide and the deduced protein molecular mass of one subunit was 28.1 kDa. The recombinant glucose dehydrogenase (rGDH-G3) was functionally expressed inEscherichia coli. The results revealed that expressed rGDH-G3 had a high specific activity of 371.9 U/mg at 25°C and pH 8.0, with oxidized nicotinamide adenine dinucleotide (NAD+) as the cofactor. The enzyme was optimally active at 40°C and pH 9.0. The enzyme displayed broad specificity for other sugars such as D-galactose or maltose. The catalytic efficiency of the rGDH-G3 would be improved 4 times when oxidized nicotinamide adenine dinucleotide phosphate (NADP+) was used as cofactor instead of NAD+.
Key words: Bacillus sp. G3, enzymatic property, glucose dehydrogenase, inverse polymerase chain reaction (IPCR), optimal pH.
gdh, Glucose dehydrogenase gene; GDH, glucose dehydrogenase; GDH-G3, glucose dehydrogenase from Bacillus sp. G3; PCR, polymerase chain reaction; IPCR, inverse PCR; ORF, open reading frame; rGDH-G3, recombinant glucose dehydrogenase; NAD+, oxidized nicotinamide adenine dinucleotide; NADP+, oxidized nicotinamide adenine dinucleotide phosphate; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis
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