A highly inducible β-galactosidase from Enterobacter sp.

Abstract

Enterobacter sp. 3TP2A isolated from a petroleum station was found to produce a novel, highly inducible mesophilic intracellular β-galactosidase in the presence of lactose up to 76.5 U mg-1. The enzyme was purified to 17.3-fold after gel permeation chromatography with a yield of approximately 11 %. The optimum pH and temperature values of the purified enzyme were found to be 8.0–9.0 and 35 °C, respectively. The molecular weight of the enzyme was approx. 60 kDa with a single band by both SDS-PAGE and native-PAGE, and estimated by gel filtration chromatography. The enzyme was inhibited by Zn2+ and EDTA, while Cu2+ had strong inhibitory effect even at low concentrations. Activation by Mg2+ and inhibition by EDTA show that the enzyme is metal-dependent or a metalloenzyme. The enzyme was slightly activated by 2-mer­captoethanol, while slightly inhibited by iodoacetamide. On the other hand, PCMB inhibited the enzymatic activity to a great extent, whereas it was com­pletely inhibited by N-ethylmaleimide. The Vmax and Km values were calcul­ated as 0.701 μmol min-1 and 0.104 mM, respectively. The results indicated that the β-galactosidase Enterobacter sp. 3TP2A might well be a good candi­date for use in biotechnology, particularly in the area of environment and health.