A Thermostable Fe/Mn SOD of Geobacillus Sp. PCH100 Isolated from Glacial Soil of Indian Trans-Himalaya Exhibits Activity in the Presence of Common Inhibitors.

Superoxide dismutases are the enzymes involved in dismutation of superoxide radicals into oxygen and hydrogen peroxide. The present work reports a thermostable Fe/Mn SOD of Geobacillus sp. strain PCH100 (GsSOD) isolated from glacial soil. Purified recombinant GsSOD is a dimeric protein of similar to 57 kDa that exhibited highest activity at a temperature of 10 degrees C and pH of 7.8. Maximum enzyme velocity and Michaelis constant of the GsSOD were 1098.90 units/mg and 0.62 mu M, respectively. At 80 degrees C, thermal inactivation rate constant and half-life of GsSOD were 3.33 x 10(-3) min(-1) and 208 min, respectively. Interestingly, GsSOD tolerated a temperature of 100 degrees C and 130 degrees C up to 15 min and 5 min, respectively. Circular dichroism and differential scanning calorimetry confirmed thermostable nature of GsSOD. Apoenzyme of GsSOD regained enzymatic activity in the presence of Fe2+ and Mn2+ as metal ion cofactors. GsSOD was stable under varying concentrations of chemicals, namely ethylenediaminetetraacetic acid, potassium cyanide, hydrogen peroxide, chloroform-ethanol, 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate, Tween-20, Triton X-100, urea, and guanidine hydrochloride. The enzyme exhibited >70% activity in presence of 10 mM metal ions. Owing to its thermostable nature and resistance to chemical inhibitors, GsSOD is a potential enzyme for industrial applications. (C) 2021 Elsevier B.V. All rights reserved.