ONPG  (Cat.#:AYB26712)

The enzyme 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. To investigate the kinetic parameters of recombinant enzyme, the Michaelis-Menten constants (K_m), turnover numbers (k_cat), and catalytic efficiencies (k_cat/K_m) of Gal308 for ONPG and lactose are determined. The k_cat and K_m values are 464.7±7.8 s^-1 and 2.7±0.3 mM for ONPG, and 264.2±2.1 s^-1 and 7.1±0.8 mM for lactose, respectively. The k_cat/K_m value of the enzyme for ONPG (172.1 s^-1mM^-1) is 4.6-fold higher than that for lactose (37.2 s^-1mM^-1), which clearly demonstrated that the catalytic efficiency of Gal308 for ONPG is much higher than that for lactose.

The accuracy of these methods have not been independently confirmed. They are for reference only.