Characterization of soluble vs membrane-bound human placental 5'-nucleotidase.
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Klemens MR, Sherman WR, Holmberg NJ, Ruedi JM, Low MG, Thompson LF
Characterization of soluble vs membrane-bound human placental 5'-nucleotidase.
Biochem Biophys Res Commun. 1990 Nov 15;172(3):1371-7.
- PubMed ID
- 2173922 [ View in PubMed]
- Abstract
Three forms of 5'-nucleotidase purified from human placenta (two membrane-bound forms, one sensitive and one resistant to cleavage by phosphatidylinositol-specific phospholipase C, as well as a soluble form) had the same molecular weight before (73,000 Da) and after (56,000 Da) digestion with N-glycosidase F and showed similar amino acid compositions, N-terminal amino acid sequences, and KMs for IMP (9.6 to 11.9 microM). Thus, these three forms of 5'-nucleotidase appear to have very similar structures. The form sensitive to phosphatidylinositol-specific phospholipase C contained nearly 1 mol myo-inositol/mol of protein as determined by mass spectrometry, indicating a glycosyl phosphatidylinositol membrane anchor. Soluble 5'-nucleotidase contained a similar quantity of myo-inositol, suggesting that it was previously membrane-anchored via glycosyl phosphatidylinositol. The form resistant to phosphatidylinositol-specific phospholipase C contained less myo-inositol, leaving open the possibility of a third form of 5'-nucleotidase with a conventional transmembrane anchor.