The YacK gene from Yersinia enterocolitica strain 7, cloned in pET28a vector and expressed in Escherichia coli BL21 (DE3), showed laccase activity when oxidized with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and guaiacol. The recombinant laccase protein was purified and characterized biochemically with a molecular mass of approximate to 58 KDa on SDS-PAGE and showed positive zymogram with ARTS. The protein was highly robust with optimum pH 9.0 and stable at 70 degrees C upto 12 h with residual activity of 70%. Kinetic constants, K-m values, for ARTS and guaiacol were 675 mu M and 2070 mu M, respectively, with corresponding Vmax values of 0.125 mu mol/ml/min and 6500 mu mol/ml/min. It also possess antioxidative property against BSA and Cu2+/H2O2 model system. Constant pH MD simulation studies at different protonation states of the system showed ABTS to be most stable at acidic pH, whereas, diclofenac at neutral pH. Interestingly, aspirin drifted out of the binding pocket at acidic and neutral pH, but showed stable binding at alkaline pH. The biotransformation of diclofenac and aspirin by laccase also corroborated the in silica results. This is the first report on biotransformation of non-steroidal anti-inflammatory drugs (NSAIDs) using recombinant Iaccase from gut bacteria, supported by in silica simulation studies. (C) 2015 Elsevier Inc. All rights reserved.