Purification, characterization, molecular modeling and docking study of fish waste protease.

In the present study, the alkaline protease has been extracted from the fish processing waste using ammonium sulphate fractionation followed by ion-exchange chromatography on sephadex G-25 and on DEAE column with a 4.0 fold increase in purification of yield 7.7%. The molecular weight of the purified protease was found to be 33 kDa as determined by SDS-PAGE. The optimum temperature was found to be 30 °C at pH 8. The activation energy (Ea ) for casein hydrolysis and temperature quotient (Q10 ) was found to be 38.25 kJ/mol and 1.65, respectively. The kinetic constants km , Vmax , kcat, and kcat/km and thermodynamic parameters ΔH*, ΔS*, ΔG*, ΔG*E-S , and ΔG*E-T revealed high affinity of the fish protease for casein. Using CD spectroscopy it was found that the fish protease has 32.7% alpha-helical, 32.8% β-turn and 34.5% random coil. 3D structure of target protein was predicted by homology modeling. Ramachandran plot revealed that the total residues in favored, allowed and outlier regions are 96.6%, 2.3%, and 1.1% residues. The biological function of the modeled fish protease was predicted by COACH based on the I-TASSER model, suggests that the fish protease may be exploited as biocatalyst in various industrial applications and processes. AutoDock 4.2.6. was used to study the protein-ligand interactions, which may lead to the discovery of novel semisynthetic enzymes from renewable biowaste.