Extracellular pyrophosphate (ePPi) was first identified as a key endogenous inhibitor of mineralisation in the 1960's by Fleisch and colleagues. The main source of ePPi seems to be extracellular ATP which is continually released from cells in a controlled way. ATP is rapidly broken down by enzymes including ecto-nucleotide pyrophosphatase/phosphodiesterases to produce ePPi. The major function of ePPi is to directly inhibit hydroxyapatite formation and growth meaning that this simple molecule acts as the body's own "water softener". However, studies have also shown that ePPi can influence gene expression and regulate its own production and breakdown. This review will summarise our current knowledge of ePPi metabolism and how it acts to prevent pathological soft tissue calcification and regulate physiological bone mineralisation.

中文翻译：

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细胞外焦磷酸盐：人体的“软水剂”

Fleisch 及其同事在 1960 年代首次将细胞外焦磷酸盐 (ePPi) 确定为矿化的关键内源性抑制剂。ePPi 的主要来源似乎是细胞外 ATP，它以受控方式从细胞中持续释放。ATP 被包括胞外核苷酸焦磷酸酶/磷酸二酯酶在内的酶迅速分解以产生 ePPi。ePPi 的主要功能是直接抑制羟基磷灰石的形成和生长，这意味着这种简单的分子充当人体自身的“软水剂”。然而，研究也表明 ePPi 可以影响基因表达并调节其自身的产生和分解。本综述将总结我们目前对 ePPi 代谢的了解，以及它如何防止病理性软组织钙化和调节生理性骨矿化。