Interaction of Uranium(VI) with α‑Amylase and Its Implication for Enzyme Activity
Interaction of Uranium(VI) with α‑Amylase and Its Implication for Enzyme Activity
Barkleit, A.; Hennig, C.; Ikeda-Ohno, A.
Because of its chemo- and radiotoxicity, the incorporation of uranium into human body via ingestion potentially poses a
serious health risk. When ingested, the gastrointestinal fluids are the primary media to interact with uranium, eventually influencing and even determining its biochemical behavior in the gastrointestinal tract and thereafter. The chemical interactions between uranium and the components of gastrointestinal fluids are, however, poorly understood to date. In this study, the complexation of uranium(VI) (as the uranyl ion, UO22+) with the protein α-amylase, one of the major enzymes in saliva and pancreatic juices, was investigated over a wide range of pH or uranium/α-amylase concentrations covering physiological conditions. Macroscopic sorption experiments suggested a strong and fast complexation of UO22+ to α-amylase between pH 5 and 7. Potentiometric titration was employed to determine the complex stability constants for the relevant UO22+ α-amylase complexes, which is crucial for reliable thermochemical modeling to assess the potential health risk of uranium. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that α-amylase is interacting with UO22+ primarily via its carboxylate groups presumably from the aspartic acid and glutamic acid side chains. The effect of UO22+ on the enzyme activity was also investigated to understand the potential implication of uranium for the in vivo functions of the digestive fluids, indicating that the presence of uranium inhibits the enzyme activity. This inhibitory effect can be, however, suppressed by an excess of calcium.
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 27359) publication
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Chemical Research in Toxicology 31(2018), 1032-1041
Online First (2018) DOI: 10.1021/acs.chemrestox.8b00106
Cited 8 times in Scopus
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Publ.-Id: 27359