Biodegradation of phthalic acid esters (PAEs) and in silico structural characterization of mono-2-ethylhexyl phthalate (MEHP) hydrolase on the basis of close structural homolog

• Published in: Journal of hazardous materials 2017-09, Vol.338, p.11-22
• Main Authors: Singh, Neha, Dalal, Vikram, Mahto, Jai Krishna, Kumar, Pravindra
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Biodegradation; Biodegradation, Environmental; Catalytic Domain; Computer Simulation; DEHP; Diethylhexyl Phthalate - analogs & derivatives; Diethylhexyl Phthalate - chemistry; Diethylhexyl Phthalate - metabolism; Esters - chemistry; Gas Chromatography-Mass Spectrometry; Hydrolases - chemistry; Hydrolases - metabolism; MEHP hydrolase; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Molecular docking; Molecular Docking Simulation; Molecular Structure; Phthalate monoesters; Pseudomonas - enzymology; Pseudomonas - genetics; Pseudomonas - metabolism; Pseudomonas - ultrastructure; RNA, Ribosomal, 16S - genetics; Soil Pollutants - metabolism; Species Specificity
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2017.04.055

•Isolation of three phthalate degrading bacteria from plastic contaminated soil.•Identification of tentative DEHP degradation pathway in Pseudomonas sp. PKDE1.•In silico model prediction of MEHP hydrolase and docking with phthalate monoesters.•Role of catalytic residues of MEHP hydrolase in phthalate monoesters degradation. Three bacterial strains capable of degrading phthalates namely Pseudomonas sp. PKDM2, Pseudomonas sp. PKDE1 and Pseudomonas sp. PKDE2 were isolated and characterized for their degradative potential. These strains efficiently degraded 77.4%–84.4% of DMP, 75.0%–75.7% of DEP and 71.7%–74.7% of DEHP, initial amount of each phthalate is 500mgL−1 of each phthalate, after 44h of incubation. GC–MS results reveal the tentative DEHP degradation pathway, where hydrolases mediate the breakdown of DEHP to phthalic acid (PA) via an intermediate MEHP. MEHP hydrolase is a serine hydrolase which is involved in the reduction of the MEHP to PA. The predicted 3D model of MEHP hydrolase from Pseudomonas mosselii was docked with phthalate monoesters (PMEs) such as MEHP, mono-n-hexyl phthalate (MHP), mono-n-butyl phthalate (MBP) and mono-n-ethyl phthalate (MEP), respectively. Docking results show the distance between the carbonyl carbon of respective phthalate monoester and the hydroxyl group of catalytic serine lies in the range of 2.9 to 3.3Å, which is similar to the ES complex of other serine hydrolases. This structural study highlights the interaction and the role of catalytic residues of MEHP hydrolase involved in the biodegradation of PMEs to phthalate.