Characteristics of the Included Studies.

♦ NA: Data obtained from abstract
Legend: OR: odds ratio; HR: harzard ratio; CDAD: Clostridium difficile-associated diarrhea; PPI: Proton pump inhibitor; H2RA: VA: Veteran Affairs; D: Durham County, P: Prospective; R: Retrospective, ABX: Antibiotic; GPRD: General Practice Research Database; ICU: Intensive care unit
Metabolic processes are controlled by a variety of enzymes. For instance, cytochrome P450 monooxygenase could detoxify herbicides such as fenoxaprop-ethyl, diclofop-methyl, and bentazon in plants [22], [23]. Polyphenol oxidase (PPO), commonly found in fungi and plants, refers to a group of enzymes that catalyze the oxidation of phenolic compounds [24]. Peroxidase (POD), another type of oxidative enzyme commonly present in plant and animal tissues, can oxidize phenols and aromatic amines in the presence of hydrogen peroxide. In contrast, the oxidation of phenolic compounds by PPO requires the presence of oxygen gas [25]. Both PPO and POD play important roles in the metabolism of aromatic compounds in soil and water [26], [27]. However, little information is available regarding their function in the metabolism of PAHs by plants.