Fluorometric determination of the activity of inorganic pyrophosphatase and its inhibitors by exploiting the peroxidase mimicking properties of a two-dimensional metal organic framework

A copper(II)-based two-dimensional metal-organic framework with nanosheet structure (CuBDC NS) that possesses peroxidase (POx) mimicking activity was prepared. In the presence of hydrogen peroxide, the system catalyses the oxidation of terephthalic acid to a blue-fluorescent product (excitation = 315 nm; emission = 425 nm). Pyrophosphate has a very strong affinity for Cu ²⁺ ion and blocks the POx-mimicking activity of the CuBDC NS. If, however, inorganic pyrophosphatase is present, the POx mimicking activity is gradually restored because pyrophosphate is hydrolyzed. The findings were used to design a method for the determination of the activity of inorganic pyrophosphatase by fluorometry. Fluorescence increases linearly in the 1–50 mU·mL ⁻¹  inorganic pyrophosphatase activity range. The limit of detection is 0.6 mU·mL ⁻¹ (S/N = 3). [Figure not available: see fulltext.].