Egli Christine M, Natumi Regiane S, Jones Martin R, Janssen Elisabeth M-L
Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Switzerland; Eawag, Swiss Federal Institute of Aquatic Science and Technology, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Switzerland.
Chimia (Aarau). 2020 Mar 25;74(3):122-128. doi: 10.2533/chimia.2020.122.
Harmful cyanobacterial blooms in freshwater ecosystems produce bioactive secondary metabolites including cyanopeptides that pose ecological and human health risks. Only adverse effects of one class of cyanopeptides, microcystins, have been studied extensively and have consequently been included in water quality assessments. Inhibition is a commonly observed effect for enzymes exposed to cyanopeptides and has mostly been investigated for human biologically relevant model enzymes. Here, we investigated the inhibition of ubiquitous aquatic enzymes by cyanobacterial metabolites. Hydrolytic enzymes are utilized in the metabolism of aquatic organisms and extracellularly by heterotrophic bacteria to obtain assimilable substrates. The ubiquitous occurrence of hydrolytic enzymes leads to the co-occurrence with cyanopeptides especially during cyanobacterial blooms. Bacterial leucine aminopeptidase and alkaline phosphatase were exposed to cyanopeptide extracts of different cyanobacterial strains ( wild type and microcystin-free mutant, ) and purified cyanopeptides. We observed inhibition of aminopeptidase and phosphatase upon exposure, especially to the apolar fractions of the cyanobacterial extracts. Exposure to the dominant cyanopeptides in these extracts confirmed that purified microcystins, aerucyclamide A and cyanopeptolin A inhibit the aminopeptidase in the low mg L range while the phosphatase was less affected. Inhibition of aquatic enzymes can reduce the turnover of nutrients and carbon substrates and may also impair metabolic functions of grazing organisms.
淡水生态系统中有害的蓝藻水华会产生具有生物活性的次生代谢产物，包括对生态和人类健康构成风险的环肽。只有一类环肽——微囊藻毒素的不利影响得到了广泛研究，因此被纳入了水质评估。抑制作用是环肽作用于酶时常见的效应，并且大多是针对与人类生物学相关的模型酶进行研究的。在此，我们研究了蓝藻代谢产物对普遍存在的水生酶的抑制作用。水解酶在水生生物的新陈代谢中发挥作用，异养细菌也会在细胞外利用水解酶来获取可同化的底物。水解酶的普遍存在导致其与环肽同时出现，尤其是在蓝藻水华期间。将细菌亮氨酸氨肽酶和碱性磷酸酶暴露于不同蓝藻菌株（野生型和无微囊藻毒素突变体）的环肽提取物以及纯化的环肽中。我们观察到暴露后氨肽酶和磷酸酶受到抑制，尤其是对蓝藻提取物的非极性部分。暴露于这些提取物中的主要环肽证实，纯化的微囊藻毒素、铜绿环肽A和环肽菌素A在低毫克/升范围内会抑制氨肽酶，而磷酸酶受影响较小。水生酶的抑制作用会降低营养物质和碳底物的周转率，还可能损害捕食生物的代谢功能。
