A temperature and salt-tolerant L-glutaminase from gangotri region of uttarakhand himalaya: enzyme purification and characterization.

Purification and characterization of halotolerant, thermostable alkaline L-glutaminase from a Bacillus sp. LKG-01 (MTCC 10401), isolated from Gangotri region of Uttarakhand Himalaya, is being reported in this paper. Enzyme has been purified 49-fold from cell-free extract with 25% recovery (specific activity 584.2 U/mg protein) by (NH₄)₂SO₄ precipitation followed by anion exchange chromatography and gel filtration. Enzyme has a molecular weight of 66 kDa. L-Glutaminase is most active at pH 11.0 and stable in the pH range 8.0-11.0. Temperature optimum is 70 °C and is completely stable after 3 h pre-incubation at 50 °C. Enzyme reflects more enhanced activity with 1-20% (w/v) NaCl, which is further reduced to 80% when NaCl concentration was increased up to 25%. L-Glutaminase is almost active with K⁺, Zn²⁺, and Ni²⁺ ions and K(m) and V(max) values of 240 μM and 277.77 ± 1.1 U/mg proteins, respectively. Higher specific activity, purification fold, better halo-tolerance, and thermostability would make this enzyme more attractive for food fermentation with respect to other soil microbe derived L-glutaminase reported so far.