Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, University of South China, Hengyang, China.
Xiangya School of Public Health, Central South University, Changsha, China.
Ecotoxicol Environ Saf. 2022 May 1;236:113436. doi: 10.1016/j.ecoenv.2022.113436. Epub 2022 Mar 31.
Microcystins (MCs) are the most common and toxic cyanotoxins that are hazardous to human health and ecosystems. Microcystinase is the enzyme in charge of the initial step in the biodegradation of MCs. The characterization, application conditions, and detoxification mechanisms of microcystinase from an indigenous bacterium Sphingopyxis sp. YF1 towards MC-LR were investigated in the current study. The microcystinase gene of strain YF1 was most similar to Sphingomonas sp. USTB-05 and contained a CAAX-family conversed abortive Infection (ABI) domain. The microcystinase was successful obtained and purified by overexpression in Escherichia coli. The highest degradation rate of MC-LR was 1.0 μg/mL/min under the optimal condition of 30 ℃, pH 7, 20 μg/mL MC-LR, and 400 μg/mL microcystinase. The MC-degrading product was identified as linearized MC-LR, which possessed a much lower inhibitory activity against protein phosphatase 2A than MC-LR. Microcystinase interacted with MC-LR via amino acid residues involved in through the formation of conventional Hydrogen Bond, Pi-Pi T-shapes, Van der Waals force, and so on. The optimal MC-degrading condition of pure microcystinase and its detoxification mechanisms against MC-LR were revealed. The toxicity of purified linearized MC-LR was explored for the first time. These findings suggest that pure microcystinase may efficiently detoxify MCs and it is promising in the bioremediation of MC-polluted environments.
微囊藻毒素（MCs）是最常见且毒性最强的蓝藻毒素，对人类健康和生态系统构成危害。微囊藻酶是负责 MCs 生物降解初始步骤的酶。本研究考察了一株土著细菌 Sphingopyxis sp. YF1 产生的微囊藻酶对 MC-LR 的特征、应用条件和解毒机制。菌株 YF1 的微囊藻酶基因与 Sphingomonas sp. USTB-05 最为相似，含有 CAAX 家族的保守失败感染（ABI）结构域。通过在大肠杆菌中的过表达成功获得并纯化了微囊藻酶。在 30℃、pH7、20μg/mL MC-LR 和 400μg/mL 微囊藻酶的最佳条件下，MC-LR 的降解率最高可达 1.0μg/mL/min。鉴定出的 MC 降解产物为线性化 MC-LR，其对蛋白磷酸酶 2A 的抑制活性明显低于 MC-LR。微囊藻酶通过参与氢键、Pi-Pi T 型结构、范德华力等常规相互作用与 MC-LR 相互作用。揭示了纯微囊藻酶的最佳 MC 降解条件及其对 MC-LR 的解毒机制。首次探讨了纯化线性化 MC-LR 的毒性。这些发现表明，纯微囊藻酶可能有效地解毒 MCs，在 MC 污染环境的生物修复中具有广阔的应用前景。
