Extracellular enzymes contribute substantially to the remineralisation of organic matter in aquatic systems. Marine invertebrates release endogenous enzymes through activities such as sloppy feeding or egestion, but the significance of such processes is widely unexplored. We compared functional key properties such as activity, stability, and apparent molecular masses of extracellular phosphatases from faeces of the marine crustaceans Idotea balthica , Palaemon varians , and Homarus gammarus with those of their digestive organs. A fluorescent substrate was used to examine enzyme activity qualitatively on agarose plates and quantitatively in microplate assays. Apparent molecular masses and enzyme stability were examined by native substrate gel electrophoresis (NSGE). Active extracellular phosphatase were present in the faeces of all tested species. NSGE activity band patterns were similar in digestive tissue extracts and faeces extracts. The initial enzyme activity retained for about 2 days, but thereafter rapidly decreased. Activity band patterns of digestive organs and faeces of I. balthica remained consistent for up to 72 h. Antibiotic treatment did not reduce phosphatase activity in the faeces of I. balthica and H. gammarus but in the faeces P. varians . Because of the comparatively high activities in the faeces, the electrophoretic similarity between faeces and digestive organs, and the limited durability of the enzymes in faeces extracts, we conclude that the studied crustaceans release predominantly endogenous, rather than bacterial phosphatases through faeces. These can substantially contribute to the pool of active extracellular phosphatases and the recycling of phosphorus in aquatic systems. The wider physiological and ecological context is discussed.

中文翻译：

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无脊椎动物来源的细胞外磷酸酯酶：磷循环中被低估的参与者？

细胞外酶对水生系统中有机物的再矿化有很大贡献。海洋无脊椎动物通过马虎进食或消化等活动释放内源性酶，但此类过程的重要性尚未得到广泛探索。我们比较了来自海洋甲壳类动物 Idotea balthica、Palaemon varians 和 Homarus gammarus 的粪便的细胞外磷酸酶的活性、稳定性和表观分子量等功能关键特性与其消化器官的功能关键特性。荧光底物用于在琼脂糖板上定性检测酶活性，并在微孔板测定中定量检测酶活性。通过天然底物凝胶电泳（NSGE）检查表观分子量和酶稳定性。所有测试物种的粪便中都存在活性细胞外磷酸酶。NSGE 活性条带模式在消化组织提取物和粪便提取物中相似。最初的酶活性保持了大约 2 天，但此后迅速下降。I. balthica 消化器官和粪便的活动带模式在长达 72 小时内保持一致。抗生素处理不会降低 I. balthica 和 H. gammarus 粪便中的磷酸酶活性，但会降低 P. varians 粪便中的磷酸酶活性。由于粪便中相对较高的活性、粪便和消化器官之间的电泳相似性以及粪便提取物中酶的耐久性有限，我们得出结论，所研究的甲壳类动物主要通过粪便释放内源性磷酸酶，而不是细菌磷酸酶。这些可以极大地促进活性细胞外磷酸酶的池和水生系统中磷的再循环。讨论了更广泛的生理和生态环境。