Role of tetrachloro-1,4-benzoquinone reductase in phenylalanine hydroxylation system and pentachlorophenol degradation in Bacillus cereus AOA-CPS1

This study reports a congruent to 12.5 kDa protein tetrachloro-1,4-benzoquinone reductase (CpsD) from Bacillus cereus strain AOA-CPS1 (BcAOA). CpsD is purified to homogeneity with a total yield of 35% and specific activity of 160 U.mg(-1) of protein. CpsD showed optimal activity at pH 7.5 and 40 T. The enzyme was found to be functionally stable between pH 7.0-7.5 and temperature between 30 T and 35 degrees C. CpsD activity was enhanced by Fe2+ and inhibited by sodium azide and SDS. CpsD followed Michaelis-Menten kinetic exhibiting an apparent v(max),(km), k(cat), and k(cat)/ K-m values of 0.071 mu mol.s(-1). 94 mu mol, 0.029 s(-1) and 3.13 x 10(-4) s(-1).mu mol(-1) respectively, for substrate tetrachloro-1,4-benzoguinone. The bioinformatics analysis indicated that CpsD belongs to the PCD/DCoH superfamily, with specific conserved protein domains of pterin-4 alpha-carbinolamine dehydratase (PCD). This study proposed that CpsD catalysed the reduction of tetrachloro-1,4-benzoquinone to tetrachloro-p-hydroquinone and released the products found in phenylalanine hydroxylation system (PheOHS) via a Ping-Pong or atypical ternary mechanism: and regulate expression of phenylalanine 4-monooxygenase by blocking reverse flux in BcAOA PheOHS using a probable Yin-Yang mechanism. The study also concluded that CpsD may play a catalytic and regulatory role in BcAOA PheOHS and pentachlorophenol degradation pathway. (C) 2020 Elsevier B.V. All rights reserved.