Red Sea Atlantis II brine pool nitrilase with unique thermostability profile and heavy metal tolerance

Abstract

Background: Nitrilases, which hydrolyze nitriles in a one-step reaction into carboxylic acids and ammonia, gained increasing attention because of the abundance of nitrile compounds in nature and their use in fine chemicals and pharmaceutics. Extreme environments are potential habitats for the isolation and characterization of extremozymes including nitrilases with unique resistant properties. The Red Sea brine pools are characterized by multitude of extreme conditions. The Lower Convective Layer (LCL) of the Atlantis II Deep Brine Pool in the Red Sea is characterized by elevated temperature (68 °C), high salt concentrations (250 ‰), anoxic conditions and high heavy metal concentrations. Results: We identified and isolated a nitrilase from the Atlantis II Deep Brine Pool in the Red Sea LCL. The isolated 338 amino-acid nitrilase (NitraS-ATII) is part of a highly conserved operon in different bacterial phyla with indiscernible function. The enzyme was cloned, expressed and purified. Characterization of the purified NitraS-ATII revealed its selectivity towards dinitriles, which suggests a possible industrial application in the synthesis of cyanocarboxylic acids. Moreover, NitraS-ATII showed higher thermal stability compared to a closely related nitrilase, in addition to its observed tolerance towards high concentrations of selected heavy metals. Conclusion: This enzyme sheds light on evolution of microbes in the Atlantis II Deep LCL to adapt to the diverse extreme environment and can prove to be valuable in bioremediation processes.