Inhibition Properties of Arylsulfatase and β-Glucuronidase by Hydrogen Peroxide, Hypochlorite, and Peracetic Acid

Abstract

Arylsulfatase and β-glucuronidase are two important enzymes in humans, which play an important role in the dynamic equilibrium of steroidal estrogens. This work probably for the first time reported that hydrogen peroxide (H2O2), hypochlorite, and peracetic acid (PAA) could effectively inhibit the activities of arylsulfatase and/or β-glucuronidase. The 50% of inhibitions (IC50) of H2O2, hypochlorite, and PAA on arylsulfatase were found to be 142.90 ± 9.00, 91.83 ± 10.01, and 43.46 ± 2.92 μM, respectively. The corresponding IC50 values of hypochlorite and PAA on β-glucuronidase were 704.90 ± 41.40 and 23.26 ± 0.82 μM, whereas H2O2 showed no inhibition on β-glucuronidase. The inhibitions of arylsulfatase and/or β-glucuronidase by these three chemicals were pH-dependent. It was further revealed that the inhibitions of hypochlorite on both arylsulfatase and β-glucuronidase were irreversible. On the contrary, the inhibitions by H2O2 and PAA were reversible. In addition, the inhibition by H2O2 was competitive and that by PAA was noncompetitive. In general, H2O2 and hypochlorite can be endogenously produced in humans, which suggested that the two compounds are potential endocrine disruption compounds (EDCs) as they can cause endocrine disruption via the inhibition of arylsulfatase and β-glucuronidase. This work further indicated that any agent that can induce the production of H2O2 or hypochlorite in humans is a potential EDC, which explains why some EDCs with very weak or no estrogenic potency can cause endocrine disruption, which is confirmed in epidemiological studies.

Activity measurement of arylsulfatase and β‐glucuronidase in activated sludge: HPLC‐based versus classical spectrophotometric method

“…The spectrophotometric method was performed based on our previous work (Zhang et al, 2020; Zhong et al, 2021). Briefly, arylsulfatase/β‐glucuronidase activity was estimated by measuring the amount of pNP released from pNPS or pNPG.…”

“…Hence, the enzyme activity estimation of the spectrophotometric method is based on the enzymic hydrolysate pNP, which cannot monitor the change of pNPS or pNPG. The enzyme activity of arylsulfatase/ β-glucuronidase is often defined as the absorbance equivalent of 1 μmol pNP produced per hour per milliliter of sample at 37 C. Although the enzyme activity of arylsulfatase/β-glucuronidase for soil sample is often estimated with a reaction time of 1 h (Jung et al, 2012;Tabatabai & Bremner, 1970;Zhang et al, 2020;Zhong et al, 2021), the reaction time for activated sludge system is normally set for several hours. For example, in the work of Ben et al (2017), the reaction time was set for 5 h, while in Ternes et al (1999), the reaction time was 6.7 h. Theoretically, pNP produced from pNPS or pNPG via enzyme hydrolysis may encounter part biodegradation during the period of determination process.…”