Biochemical, thermodynamic and structural characteristics of a biotechnologically compatible alkaline protease from a haloalkaliphilic, Nocardiopsis dassonvillei OK-18

This report describes purification strategies, biochemical properties and thermodynamic analysis of an alkaline serine protease from a marine actinomycete, Nocardiopsis dassonvillei strain OK-18. The solvent tolerance, broad thermal-pH stability, favourable kinetics and thermodynamics suggest stability of the enzymatic reaction. The enzyme was active in the range of pH 7-12 and 37-90 degrees C optimally at pH 9 and 70 degrees C. The deactivation rate constant (Kd), half-life (t1/2), enthalpy (Delta H*), entropy (Delta S*), activation energy (E) and change in free energy (Delta G*) suggested stability and spontaneity of the reaction. beta-Sheets as revealed by the Circular dichroism (CD) spectroscopy, were the major elements in the secondary structure of the enzyme, while Fourier-transform infrared spectroscopy (FTIR) indicated the presence of amide I and amide II. Based on the liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToE-MS) analysis, the amino add sequence had only 38% similarity with other proteases of Nocardiopsis strains, suggesting its novelty. The Ramachandran Plot revealed the location of the amino add residues in the most favored region.The blood de-staining, gelatin hydrolysis. silver recovery and deproteinization of crab shells established the biotechnological potential of the enzyme. (C) 2020 Elsevier B.V. All rights reserved.