Tobacco etch virus (TEV) protease is a 27‐kDa catalytic domain of the polyprotein nuclear inclusion a (NIa) in TEV, which recognizes the specific amino acid sequence ENLYFQG/S and cleaves between Q and G/S. Despite its substrate specificity, its use is limited by its autoinactivation through self‐cleavage and poor solubility during purification. It was previously reported that T17S/N68D/I77V mutations improve the solubility and yield of TEV protease and S219 mutations provide protection against self‐cleavage. In this study, we isolated TEV proteases with S219N and S219V mutations in the background of T17S, N68D, and I77V without the inclusion body, and measured their enzyme kinetics. The k _cat of two isolated S219N and S219V mutants in the background of T17S, N68D, and I77V mutations was highly increased compared to that of the control, and S219N was twofold faster than S219V without K _m change. This result indicates that combination of these mutations can further enhance TEV activity.

Persistent organic pollutants (POPs) are lipid-soluble toxins that are not easily degraded; therefore, they accumulate in the environment and the human body. Several studies have indicated a correlation between POPs and metabolic diseases; however, their effects on mitochondria as a central organelle in cellular metabolism and the usage of mitochondria as functional markers for metabolic disease are barely understood. In this study, a zebrafish model system was exposed to two subclasses of POPs, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), under two different conditions (solitary OCPs or OCPs with PCBs (Aroclor 1254)), and changes in the oxidative stress marker levels and mitochondrial enzyme activities in the electron transport chain of the tail were measured to observe the correlation between POPs and representative biomarkers for metabolic disease. The results indicated different responses upon exposure to OCPs and OCPs with Aroclor 1254, and accelerated toxicity was observed following exposure to mixed POPs (OCPs with Aroclor 1254). Males were more sensitive to changes in the levels of oxidative stress markers induced by POP exposure, whereas females were more susceptible to the toxic effects of POPs on the levels of mitochondrial activity markers. These results demonstrate that the study reflects real environmental conditions, with low-dose and multiple-toxin exposure for a long period, and that POPs alter major mitochondrial enzymes’ functions with an imbalance of redox homeostasis in a sex-dependent manner.

Plastics are widely used worldwide due to their convenience. However, microplastics (MPs) accumulation poses a serious threat to ecosystem health. Therefore, understanding the effects of MPs on living organisms within their native ecosystem is crucial. Previous studies have primarily focused on the impacts of MPs in aquatic environments, whereas the effects of MPs on terrestrial ecosystems have remained largely understudied. Therefore, our study assessed the impacts of MPs on soil ecosystems by characterizing their toxic effects on earthworms (Eisenia fetida). Here, we exposed earthworms to two representative plastics within soil environments: polyvinyl chloride (PVC) and low-density polyethylene (LDPE). Given the known link between MPs and oxidative stress, we next quantified oxidative stress markers and mitochondrial function to assess the effects of MPs on the redox metabolism of earthworms. Mitochondria are crucial metabolic organelles that generate reactive oxygen species via uncontrolled ATP production. Our findings demonstrated that MPs exert different effects depending on their type. Neither the PVC-exposed groups nor the LDPE-exposed groups exhibited changes in oxidative stress, as worked by the action of superoxide dismutase (SOD) and glutathione (GSH). While treatment of the two types of MP did not significantly affect the amount of reactive oxygen species/reactive nitrogen species (ROS/RNS) generated, PVC exhibited a more pronounced effect on antioxidant system compared to LDPE. However, mitochondrial function was markedly decreased in the group exposed to high LDPE concentrations, suggesting that the examined LDPE concentrations were too low to activate compensatory mechanisms. Collectively, our findings demonstrated that exposure of MPs not only influences the antioxidant defense mechanisms of earthworms but also alters their mitochondrial function depending on their types.