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Simultaneous analysis of ATP, ADP, AMP, and other purines in human erythrocytes by high-performance liquid chromatography

1980; Elsevier BV; Volume: 181; Issue: 1 Linguagem: Inglês

10.1016/s0378-4347(00)81276-1

1872-812X

Paul D. Schweinsberg, Ti Li Loo,

Calcium signaling and nucleotide metabolism

Ecto-5′-nucleotidases are glycosyl phosphatidylinositol (GPI)-linked membrane-bound glycoproteins that convert extracellular AMP to adenosine. They play important roles in the inflammatory response where they modulate levels of pro-inflammatory extracellular ATP and anti-inflammatory extracellular adenosine. They are found in the saliva of blood feeding insects and also have a role in male reproduction. Drosophila possesses five genes with eight alternative transcripts encoding proteins with sequence homology to mammalian ecto-5′-nucleotidases. Here we show that two of them – NT5E-1 (CG4827) and NT5E-2 (CG30104) – are GPI-linked proteins with ecto-5′-nucleotidase activity but that they can also be released from the GPI anchor and exhibit secreted 5′-nucleotidase activity in growth media. The third locus in the cluster, CG30103, most likely also encodes a GPI-anchored membrane-bound protein but without 5′-nucleotidase activity, possibly due to the numerous substitutions in the amino acid sequence. Together with NT5E-2, CG30103 is also expressed in the testis offering an interesting model to investigate ecto-5′-nucleotidase enzymatic and extra-enzymatic function in male reproduction. CG42249 locus encoding two alternative transcripts is sequentially similar to family of apyrases related to 5′-nucleotidases and we show here that together with CG5276 belonging to another family of calcium-activated nucleotidases function as apyrases converting extracellular ATP to ADP and AMP. The last locus, CG11883, encodes most likely a cytoplasmic/mitochondrial protein.