Inhibition of digestive enzyme activities by copper in the guts of various marine benthic invertebrates
作者:Zhen Chen、Lawrence M. Mayer、Donald P. Weston、Michael J. Bock、Peter A. Jumars
DOI:10.1002/etc.5620210618
日期:2002.6
Digestive systems of deposit and suspension feeders can be exposed to high concentrations of copper (Cu) by ingestion of contaminated sediments. We assessed a potential impact of this Cu exposure on digestive enzyme activities in a wide range of benthic organisms by monitoring enzyme activities in their gut fluids during in vitro titrations with dissolved Cu, which mimics Cu solubilization from sediments
沉积物和悬浮进料器的消化系统可能会因摄入受污染的沉积物而暴露于高浓度的铜 (Cu) 中。我们通过在体外用溶解的铜滴定期间监测其肠道液中的酶活性,评估了这种铜暴露对各种底栖生物消化酶活性的潜在影响,这模拟了沉积物中的铜溶解。增加Cu 抑制消化蛋白酶活性的阈值,这在生物体之间差异很大,从棘皮动物的8 microM 到一壳虫的0.4 M。需要更多的铜来抑制含有较高氨基酸浓度的肠道中的蛋白酶,因为氨基酸上的强铜结合位点会阻止铜与酶活性位点的相互作用。蛋白酶、酯酶、脂肪酶的阈值铜浓度相似,和α-和β-葡萄糖苷酶,表明相同的抑制机制。铜在较低的 pH 值下抑制酶的效果较差,这表明质子可以与铜离子竞争结合酶活性位点,或者酶的构象在较低的 pH 值下不太容易受到铜的抑制。这些结果导致了一个违反直觉的结论,即具有低酶活性、低氨基酸浓度和高 pH 值的沉积物喂料器最容易受到这种机制的沉积铜的伤害,尽管它们比具