Functional Characterization of a Novel Amidase Involved in Biotransformation of Triclocarban and its Dehalogenated Congeners in Ochrobactrum sp. TCC-2

Abstract

Haloaromatic antimicrobial triclocarban (3,4,4'-trichlorocarbanilide, TCC) is a refractory contaminant which is frequently detected in various aquatic and sediment environments globally. However, few TCC-degrading communities or pure cultures have been documented, and functional enzymes involved in TCC biodegradation hitherto have not yet been characterized. In this study, a bacterial strain, Ochrobactrum sp. TCC-2, capable of degrading TCC under both aerobic and anaerobic conditions was isolated from a sediment sample. A novel amidase gene (tccA), responsible for the hydrolysis of the two amide bonds of TCC and its dehalogenated congeners 4,4'-dichlorocarbanilide (DCC) and carbanilide (NCC) to more biodegradable chloroaniline or aniline products, was cloned and characterized. TccA shares low amino acid sequence identity (27 to 38%) with other biochemically characterized amidases and contains the conserved catalytic triad (Ser-Ser-Lys) of the amidase signature enzyme family. TccA was stable over a pH range of 5.0 to 10.0 and at temperatures lower than 60 °C, and it was constitutively expressed in strain TCC-2. In contrast to the halogenated TCC and DCC, the nonchlorinated NCC was the preferred substrate for TccA. TccA also had hydrolysis activity to a broad spectrum of amide bonds in herbicides, insecticides, and chemical intermediates. The constitutive expression and broad substrate spectrum of TccA suggested strain TCC-2 may be potentially useful for bioremediation applications.

A Novel Degradation Mechanism for Pyridine Derivatives in Alcaligenes faecalis JQ135

“…The values were calculated via nonlinear regression fitting to the Michaelis-Menten equation using ORIGIN software version 8.5. Buffers at pH values from 4.0 to 6.0 (citric acid-sodium phosphate), 6.0 to 8.0 (KH 2 PO 4 -K 2 HPO 4 buffer), and 8.5 to 10.0 (glycine-NaOH) were used in pH dependency experiments (39). To determine enzyme activity under anaerobic conditions, PBS was purged with high-purity nitrogen (99.99% N 2 ) for 20 min to remove oxygen before the substrate was added.…”

Mineralization of the herbicide swep by a two-strain consortium and characterization of a new amidase for hydrolyzing swep

“…BbdA was identified from Aminobacter and initiates the degradation of 2,6-dichlorobenzamide [36]. TccA was identified from Ochrobactrum and is involved in the hydrolysis of triclocarban [28]. To the best of our knowledge, no amidases have been reported that initiate the degradation of swep.…”

The Novel Monocomponent FAD-dependent Monooxygenase HpaM Catalyzes the 2-Decarboxylative Hydroxylation of 5-Hydroxypicolinic Acid inAlcaligenes faecalisJQ135

“…The kinetics values were calculated via nonlinear regression fitting to the Michaelis-Menten equation. The effects of different pH (3.0 to 10.0), temperature (10 to 60°C), and metal ions on HpaM activities were determined as previously reported (29).…”