The cDNA cloning of human placental ecto‐ATP diphosphohydrolases I and II¹

Abstract

The cDNA clones of two isoforms (enzymes I and II) of human placental ecto-ATP diphosphohydrolases have been isolated based on the N-terminal amino acid (aa) sequence of the immunopurified 82 kDa protein and characterized. The cDNA clone encoding enzyme I consists of 2081 nucleotides and the predicted enzyme I consists of 517 aa residues. Enzyme I has a 5P P-UTR and an N-terminal 11 aa sequence that differ from CD39, but the rest of the sequence is the same as CD39. The hydropathy plot indicated that enzyme I has two hydrophobic regions near the N-and C-termini of the molecule. In contrast, enzyme II consists of 1814 nucleotides and the predicted protein consists of 306 aa residues. The sequence of 1^1018 nucleotides of enzyme II is identical to that of enzyme I, but the 1019^1814 nucleotide sequence is different from both enzyme I and CD39. The hydropathy plot indicated that enzyme II has one hydrophobic region near the N-terminus, suggesting that enzyme II is also anchored to the cell membrane. It is, however, likely that some of enzyme II exists as a soluble form in plasma, possibly after proteolytic processing.z 1999 Federation of European Biochemical Societies.

Cellular function and molecular structure of ecto-nucleotidases

“…At the same time, the vascular NTPDase was identified as NTPDase1 [89]. A catalytically active human variant with an N-terminal sequence of 11 amino acids differing from CD39 was cloned from a human placenta cDNA library, whereas a truncated form lacking ACR5 was catalytically inactive [90,91]. The cell biology and function of these forms has not been further elucidated.…”

“…Accordingly, transgenic mice expressing human NTPDase1 exhibited impaired platelet aggregation and were protected from thrombosis in a transplantation setting [179]. Moreover, adenovirus-mediated gene transfer of human placental NTPDase1 [91] into vascular smooth muscle cells was found to suppress thrombus formation and subsequent neointimal growth [180]. Similarly, gene transfer of this enzyme via cationic gelatin-coated stents inhibited subacute in-stent thrombosis and in addition suppressed neointimal hyperplasia and inflammation [181].…”

Purinergic signalling in the reproductive system in health and disease

“…Later, ATP diphosphohydrolase (or apyrase) was identified in human term placenta [81,198,316]. Two isoforms (enzymes I and II) of placental ecto-ATP diphosphohydrolases were later identified by cDNA cloning [263]. Four ATPases, which bind to ATP at the external surface of the membrane of syncytiotrophoblast brush boarder membranes, were described [54].…”

Purification, characterization, cloning, and expression of the chicken liver ecto‐ATP‐diphosphohydrolase

“…The majority of the ecto-ATPDases that have been cloned are closely related to CD39, a cell surface antigen that is expressed on activated lymphocytes [11,12]. CD39s from several species have 60-90% identity in their primary sequences [12][13][14][15]. Biochemical and immunolocalization studies indicated that CD39s are vascular ecto-ATPDases [16][17][18][19][20].…”