The ecto‐nucleoside triphosphate diphosphohydrolases (NTPDases) are a family of enzymes found on the cell surface and in the lumen of certain organelles, that are major regulators of purinergic signaling. Their intracellular roles, however, have not been clearly defined. NTPDase4 (UDPase, ENTPD4) is a Golgi protein potentially involved in nucleotide recycling as part of protein glycosylation, and is also found in lysosomes, where its purpose is unknown. To further our understanding of NTPDase4 function, we determined its crystal structure. The enzyme adopts a wide open, inactive conformation. Differences in the nucleotide‐binding site relative to its homologs could account for its substrate selectivity. The putative membrane‐interacting loop of cell‐surface NTPDases is drastically altered in NTPDase4, potentially affecting its interdomain dynamics at the Golgi membrane.

中文翻译：

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核苷酸代谢酶 NTPDase4 的晶体结构。

胞外核苷三磷酸二磷酸水解酶 (NTPDases) 是在细胞表面和某些细胞器的腔中发现的酶家族，它们是嘌呤能信号的主要调节剂。然而，它们的细胞内作用尚未明确定义。NTPDase4 (UDPase, ENTPD4) 是一种高尔基体蛋白，可能作为蛋白质糖基化的一部分参与核苷酸循环，也存在于溶酶体中，但其用途尚不清楚。为了进一步了解 NTPDase4 的功能，我们确定了它的晶体结构。该酶采用广泛开放的无活性构象。核苷酸结合位点相对于其同源物的差异可以解释其底物选择性。细胞表面 NTPDases 的假定膜相互作用环在 NTPDase4 中发生了巨大变化，