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Nature’s Green Catalyst for Environmental Remediation, Clean Energy Production, and Sustainable Development
Published in Miguel A. Esteso, Ana Cristina Faria Ribeiro, A. K. Haghi, Chemistry and Chemical Engineering for Sustainable Development, 2020
Benny Thomas, Divya Mathew, K. S. Devaky
Monooxygenases catalyze the oxidation of simple alkanes, complex steroids, and fatty acids.12 Monooxygenases act as biocatalysts in bioremediation process and synthetic chemistry due to their highly region selectivity and stereoselectivity on a wide range of substrates.4 These enzymes require only molecular oxygen for their activities and utilize the substrate as reducing agent.13 They utilize the substrate as reducing agent and necessitate only molecular oxygen for their activities. The main reactions catalyzed by monooxygenases include desulfurization, dehalogenation, denitrification, ammonification, hydroxylation, biotransformation, and biodegradation of various aromatic and aliphatic compounds.14 Majority of monooxygenases comprise cofactors,4 for example, flavin-dependent monooxygenases and P450 monooxygenases. Methane monooxygenase is the best one for the degradation of substituted aliphatic, aromatic, and heterocyclic hydrocarbons. Monooxygenase catalyzes oxidative dehalogenation reactions under oxygen-rich conditions whereas they consequence reductive dechlorination affording the formation of labile products under low oxygen levels. Methane monooxygenases are found in cytoplasmic membrane and cytoplasm.
Designing Metabolic Pathways for the Biodegradation of Halogenated Compounds
Published in Subhas K. Sikdar, Robert L. Irvine, Fundamentals and Applications, 2017
The most versatile and well-studied of the metallomacrocycles in Figure 4 are the iron porphoryins, or heme, cofactor. Proteins bind heme for many functions (Table 1). These include electron transfer reactions, oxygenation reactions, sulfuroxyanion reduction, and oxygen reduction (Wackett et al., 1989a). The latter biological functions, reductive chemistry, presage the ability of the heme cofactor to reduce carbon-halogen bonds. Oxygenation reactions are, on inspection of the reaction mechanism, an outgrowth of enzyme reduction of an iron-bound O2 molecule (Figure 5). Molecular oxygen is initially reduced and, in monooxygenase reactions, ultimately cleaved to release the reduced product water and generate a reactive iron-bound monoatomic oxygen species. The oxygen atom reacts with organic substrates bound by the enzyme to make oxygenated products. But the potential exists, in the absence of O2, to recruit the reductive part of heme biochemistry for metabolism of halogenated organic compounds.
Polychlorinated Biphenyls
Published in B. K. Afghan, Alfred S. Y. Chau, Analysis of Trace Organics in the Aquatic Environment, 2017
Barry G. Oliver, Robert M. Baxter, Hing-Biu Lee
A third approach is to investigate the characteristics of the enzymes responsible for the transformation of chlorobiphenyls. These, like foreign substances generally, are metabolized if at all by certain enzymes in the liver. This process is sometimes referred to as "detoxification" but it has been pointed out82,83 that the metabolites may be more toxic than the parent substances. The principal biological significance of the process is that the products are usually more hydrophilic than the parent compounds and consequently more readily excreted. The enzymes which oxidize chlorobiphenyls in animals are, in general, somewhat different from those in bacteria. The bacterial enzymes are usually dioxygenases, i.e., enzymes which incorporate both atoms of an oxygen molecule into the product (Figure 4). The animal enzymes usually only incorporate one oxygen atom into the product, and hence are called monooxygenases. They are also sometimes referred to as mixed function oxidases, because a suitable reducing agent such as reduced nicotinamide-adenine dinucleotide (NADH) is simultaneously oxidized by the other oxygen atom. The first product is thought to be an epoxide, or arene oxide,84 which can either isomerize spontaneously to a phenol or be converted by another type of enzyme, epoxide hydrase, to a dihydrodiol, which can, in turn, be oxidized to a diphenol (Figure 5).
Harnessing biodegradation potential of rapid sand filtration for organic micropollutant removal from drinking water: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Jinsong Wang, David de Ridder, Albert van der Wal, Nora B. Sutton
Biological RSF is commonly used to remove ammonium from water sources by nitrification (de Vet et al., 2011; Kors et al., 1998; van der Aa et al., 2002). Nitrification includes two biological processes, which are conducted by ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria, respectively (Niu et al., 2013). The ammonia monooxygenase enzyme has a broad substrate specificity, and not only catalyzes the oxidation reaction of ammonium, but also that of such compounds as alkanes, alkenes, aromatic and alicyclic hydrocarbons, halogenated hydrocarbons, and sulfonated hydrocarbons (Arciero et al., 1989; Hyman et al., 1988; Im & Semrau, 2011). It has been shown that nitrifying bacteria are capable of co-metabolizing various OMPs (Men et al., 2016; Roh et al., 2009; Shi et al., 2004; Sun et al., 2012).
Transformation of PPCPs in the environment: Review of knowledge and classification of pathways according to parent molecule structures
Published in Critical Reviews in Environmental Science and Technology, 2023
Kevin Bonnot, Pierre Benoit, Laure Mamy, Dominique Patureau
Hydroxylation, more commonly known as mono-oxidation, was the most observed reaction with 901 records that is 28% of the total number of reactions enumerated in the dataset (Figure 1). For biotic processes, the monooxygenase enzyme, which belongs to the cytochrome P450 enzymatic system, catalyzes the formation of a hydroxyl group -OH from an oxygen or dioxygen using NADH or NADPH (Nelson & Cox, 2000).