Laccase Inhibition by Mercury: Kinetics, Inhibition Mechanism, and Preliminary Application in the Spectrophotometric Quantification of Mercury Ions

Abstract

e noncompetitive inhibition of laccase by mercury ions is reported, in particular focusing their effect over the enzyme catalytic activity. e enzymatic kinetics were obtained for different substrates (caffeic acid, gallic acid, and catechol), where caffeic acid displayed the greatest enzymatic activity. e laccase inhibition by mercury ions permitted to establish the inhibition effect through a mixed model (that actually displayed a behavior closer to that of the noncompetitive inhibitors) when evaluated by means of UV-Vis spectrophotometry, using caffeic acid as an electron donor. A mercury concentration of 2 mM led to 35% enzymatic inhibition after only a 2-minute incubation period. is method was used for quantification of mercury ions in aqueous solution, showing a detection limit of 15 ± 1 ppm. erefore, this work presented a novel perspective for the determination of the toxic Hg(II) ions that can be readily implemented into environmental remediation methods.

Applications and immobilization strategies of the copper-centred laccase enzyme; a review

“…Laccases are inhibited by metal ions such as Hg 2+ , Fe 2+ , Ag + , Li + and Pb 2+ [ 53 , 54 , 55 ], humic acid [ 56 ], cationic quaternary ammonium detergents and small anions like halides [ 57 , 58 , 59 ], azide [ 60 , 61 ], and hydroxyl [ 62 ]. The inhibition process involves amino acid residue modification, copper chelation or conformational changes, and binding of small anions on type 2 and 3 copper hence interrupting internal electron transfer [ 58 , 59 ].…”

4-Mercaptopyridine Modified Fiber Optic Plasmonic Sensor for Sub-nM Mercury (II) Detection

“…The final calculation limit of detection (LOD) is 1.643×10 -10 M (0.1643 nM). UV spectral-SPR 3.2×10 -9 M 4×10 -9 -4×10 -8 M [20] UV-Vis spectrophotometry 7.5×10 -5 M 5×10 -5 -6×10 -4 M [22] Electrochemical-graphene oxide-DNA 1.2×10 -10 M 5×10 -10 -5×10…”

“…In 2015, Zhang et al [20] completed the detection of mercury ions using ultra violet spectroscopy and plasmon resonance technology, with a detection limit of 3.2 nM and a detection range of 4 nM -40 nM. In 2016, Lu et al [21] used electrochemistry combined with graphene oxide to increase sensitivity to detect mercury ions in water with a detection limit of 0.12 nM and a detection range of 5×10 -10 M -5×10 -8 M. In 2018, Juárez-Gómez et al [22] used spectrophotometry to detect mercury with a limit of detection (LOD) of 7.5×10 -5 M and a detection range of 5×10 -5 M -6×10 -4 M. The aforementioned methods can basically meet the current demand for the rapid detection of mercury ions, but still have problems such as complicated operation and small detection range, limiting its scope of application. As a new detection method, the fiber optic sensing technology has unique advantages of miniaturization, easy integration, anti-electromagnetic interference, high accuracy, and simple operation, and has been widely used in various applications [23].…”

Inhibition in multicopper oxidases: a critical review

“…The most commonly studied MCO inhibitors are halides and pseudohalides (e.g., azide and cyanide), [26][27][28][29][30][31] but the activity of MCOs is also affected by metal ions (e.g., Ca 2+ , Mn 2+ , Fe 2+/3+ , Co 2+ , Cu +/2+ , Ag + , Zn 2+ , Hg 2+ , Al 3+ and As 3+/5+ ), [32][33][34][35][36][37][38][39][40] reactive oxygen species (ROS) such as O 2− and H 2 O 2 , 41 reducing agents (e.g., L-cysteine, dithiothreitol, 2-mercaptoethanol), 36,[42][43][44] chelating agents (e.g., EDTA), 36,41,44,45 chaotropic agents (e.g., SDS and urea) 32,36,41,45,46 and others (e.g., short alcohols, ionic liquids and polymer end groups). 41,[47][48][49][50] Misleadingly, these enzyme inactivators are routinely surveyed alongside the more specific inhibitors of MCO activity.…”