Effect of divalent metal ions on the activity and stability of β-galactosidase isolated from Kluyveromyces lactis

This study demonstrates how β-galactosidase can be deactivated and reactivated using EDTA and divalent metal ions. The enzyme was deactivated after 20 minutes in EDTA presence. Maximal deactivation for the lowest EDTA concentration (10-3 mol.L-1) occurred in the presence of the Tris-HCl buffer. The enzyme recovered 50% of its initial activity after 10 minutes in Mg2+ presence. Mn2+ was efficient in maintaining hydrolysis reactivation of O-NPG. Co2+ demonstrated lower reactivation intensity when compared with Mg2+ and Mn2+. The enzyme gradually lost its activity when concentration was 10-2 mol.L-1. Ni2+ and Zn2+ were unable to restore the catalytic activity. Kmapp and Vmaxapp were 1.95 ± 0.05 mmol.L-1 and 5.40 ± 0.86x 10-2 mmol.min-1.mg-1. Optimal temperature and pH were 34oC and 7.5. U½ for holoenzyme was 17.5 at 30oC. U½ for apoenzyme was 11.0 at 30oC. Regarding the variation in pH, the apoenzyme proved to be more sensitive than holoenzyme.