A new enzymatic assay to quantify inorganic pyrophosphate in plasma

Lundkvist, Stefan and Niaziorimi, Fatemeh and Szeri, Flora and Caffet, Matthew and Terry, Sharon F. and Johansson, Gunnar and Jansen, Robert S. and van de Wetering, Koen (2022) A new enzymatic assay to quantify inorganic pyrophosphate in plasma. ANALYTICAL AND BIOANALYTICAL CHEMISTRY. ISSN 1618-2642

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Inorganic pyrophosphate (PPi) is a crucial extracellular mineralization regulator. Low plasma PPi concentrations underlie the soft tissue calcification present in several rare hereditary mineralization disorders as well as in more common condi- tions like chronic kidney disease and diabetes. Even though deregulated plasma PPi homeostasis is known to be linked to multiple human diseases, there is currently no reliable assay for its quantification. We here describe a PPi assay that employs the enzyme ATP sulfurylase to convert PPi into ATP. Generated ATP is subsequently quantified by firefly luciferase–based bioluminescence. An internal ATP standard was used to correct for sample-specific interference by matrix compounds on firefly luciferase activity. The assay was validated and shows excellent precision (< 3.5%) and accuracy (93–106%) of PPi spiked into human plasma samples. We found that of several anticoagulants tested only EDTA effectively blocked conversion of ATP into PPi in plasma after blood collection. Moreover, filtration over a 300,000-Da molecular weight cut-off mem- brane reduced variability of plasma PPi and removed ATP present in a membrane-enclosed compartment, possibly platelets. Applied to plasma samples of wild-type and Abcc6−/− rats, an animal model with established low circulating levels of PPi, the new assay showed lower variability than the assay that was previously in routine use in our laboratory. In conclusion, we here report a new and robust assay to determine PPi concentrations in plasma, which outperforms currently available assays because of its high sensitivity, precision, and accuracy.

Item Type: Article
Subjects: Q Science / természettudomány > QP Physiology / élettan
Depositing User: Flóra Szeri
Date Deposited: 25 Sep 2023 11:39
Last Modified: 25 Sep 2023 11:39

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