Oxidation of bisphenol A (BPA) and related compounds by the multifunctional catalytic globin dehaloperoxidase

Dehaloperoxidase (DHP) from the marine polychaete Amphitrite ornata is a multifunctional enzyme that possesses peroxidase, peroxygenase, oxidase and oxygenase activities. Herein, we investigated the reactivity of DHP B with bisphenol A (BPA) and related compounds (bisphenol E, bisphenol F, tetrachlorobisphenol A, 2,2 '-biphenol, 3,3 '- biphenol, 4,4 '-biphenol, and 3,3 '-dibromo-4,4 '-biphenol). As a previously unknown substrate for DHP B, BPA (as a representative substrate) is an endocrine disruptor widely used in polycarbonate and epoxy resins, thus resulting in human exposure. Reactivity studies with these substrates were investigated using high performance liquid chromatography (HPLC), and their corresponding oxidation products were determined by mass spec-trometry (GC-MS/ LC-MS). BPA undergoes oxidation in the presence of DHP B and hydrogen peroxide yielding two cleavage products (4-isopropenylphenol and 4-(2-hydroxypropan-2-yl)phenol), and oligomers with varying degrees of oxidation. 18O-labeling studies confirmed that the O-atom incorporated into the products was derived exclusively from water, consistent with substrate oxidation via a peroxidase-based mechanism. The X-ray crystal structures of DHP bound with bisphenol E (1.48 A), bisphenol F (1.75 A), 2,2 '-biphenol (1.90 A) and 3,3 '- biphenol (1.30 A) showed substrate binding sites are in the distal pocket of the heme cofactor, similar to other previously studied DHP substrates. Stopped-flow UV-visible spectroscopy was utilized to investigate the mechanistic details and enzyme oxidation states during substrate turnover, and a reaction mechanism is pro-posed. The data presented here strongly suggest that DHP B can catalyze the oxidation of bisphenols and biphenols, thus providing evidence of how infaunal invertebrates can contribute to the biotransformation of these marine pollutants.

Automated summary

Dehaloperoxidase (DHP) from the marine polychaete Amphitrite ornata is a multifunctional enzyme that can catalyze the oxidation of bisphenols and biphenols. The reactivity of DHP B with bisphenol A (BPA) and related compounds was studied using HPLC and GC-MS/LC-MS. The results showed that DHP B can oxidize BPA to produce cleavage products and oligomers. The crystal structures of DHP bound with different substrates were determined, and a reaction mechanism was proposed based on stopped-flow UV-visible spectroscopy. This study provides evidence of how infaunal invertebrates contribute to the biotransformation of marine pollutants.