Enzymatic analysis, structural study and molecular docking of laccase and catalase from B-subtilis SK1 after textile dye exposure

Abstract

The textile dye decolorizing efficiency of Bacillus subtilis SK1 against 70 mg/L each of Malachite Green, Methyl Orange, Rubine GFL and Red HE3B was observed as 71.7, 73.6, 74.4 and 82.6%, respectively within 3 h. UV-Vis spectroscopy, GC-MS and HPTLC analysis confirmed mineralization of model dyes into its metabolites. Physicochemical characterization confirmed acidic and hydrophilic nature of both laccase and catalase enzymes. Both enzymes contain dominant random coiled secondary structure (SOPMA tool) and intracellular location (CELLO_v.2.5), however, laccase alone contains two disulfide bridges (CYS_REC tool). The validation of constructed 3D structure (Modeller 9.19) of laccase and catalase enzymes revealed, RAMPAGE- 96.3 and 95.8% residues in favoured region, ProSA- Z score -8.2 and -9.6, respectively and ERRAT-Overall quality factor > 68. Potential energies -1.328 x 10(6) kJ/mol and - 2.685 x 10(6) kJ/mol remained constant after 1395 and 1545 steps for laccase and catalase, respectively in energy minimization. Molecular docking results showed interaction of Methyl Orange with laccase (Thr260) and catalase (Lys 48), Rubine GFL with laccase (Thr 262) and catalase (His 176) and Red HE3B with laccase (Asn 264, Thr 418, Gly 321, Thr 262 and Gly 378) and catalase (Gln 258). This study provides dye degrading potential of Bacillus subtilis strain SK1 with structurally different textile dyes and vital role of the polar amino acids of laccase and catalase in these interactions.