ONPG is a colorimetric and spectrophotometric substrate used to detect β-galactosidase activity.
To investigate the kinetic parameters of recombinant enzyme, the Michaelis-Menten constants (Km), turnover numbers (kcat), and catalytic efficiencies (kcat/Km) of Gal308 for ONPG and lactose are determined. The kcat and Km values are 464.7±7.8/s and 2.7±0.3 mM for ONPG, and 264.2±2.1/s and 7.1±0.8 mM for lactose, respectively. The kcat/Km value of the enzyme for ONPG (172.1 /s/mM) is 4.6-fold higher than that for lactose (37.2 /s/mM), which clearly demonstrated that the catalytic efficiency of Gal308 for ONPG is much higher than that for lactose. Gal308 displays high hydrolysis ability for ONPG (100%) and moderate activity for its natural substrate lactose (25.7%). However, the hydrolysis ability of the enzyme towards all other chromogenic nitrophenyl analogues is very weak, indicating that Gal308 is a β-galactosidase with narrow substrate specificity.
2-Nitrophenyl β-D-galactopyranoside , 2-硝基苯-beta-D-半乳糖苷
White or white-like powder
Colorless to light yellowicon
1. Zhang X, et al. Metagenomic approach for the isolation of a thermostable β-galactosidase with high tolerance of galactose and glucose from soil samples of Turpan Basin. BMC Microbiol. 2013 Oct 24;13:237.