NTPase encodes an intracellular NTPDase6-family nucleoside diphosphate phosphohydrolase. The 461-residue membrane-associated product hydrolyzes GDP, UDP and IDP efficiently and is localized predominantly to the endoplasmic reticulum in transfected Drosophila S2 cells. Its specificity and lumen-facing topology are consistent with nucleotide turnover associated with glycoprotein processing, rather than a general cell-surface ATP apyrase.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004382 GDP phosphatase activity | IDA PMID:19467631 The single NTPase gene of Drosophila melanogaster encodes an... | ACCEPT | Summary: GDP is a directly demonstrated substrate. Reason: The cloned Drosophila enzyme hydrolyzes GDP alongside UDP and IDP. This is substrate-resolved enzymology and supports nucleoside diphosphate hydrolysis. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. |
| GO:0004382 GDP phosphatase activity | IEA GO_REF:0000117 | ACCEPT | Summary: GDP is a directly demonstrated substrate. Reason: The cloned Drosophila enzyme hydrolyzes GDP alongside UDP and IDP. This is substrate-resolved enzymology and supports nucleoside diphosphate hydrolysis. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. |
| GO:0005576 extracellular region | IEA GO_REF:0000117 | UNDECIDED | Summary: Extracellular localization is not established for this input product. Reason: The cloned fly NTPDase6 is predominantly ER-localized and becomes accessible after detergent. A distinct secreted isoform could explain a locus-level annotation, but the present 461-residue membrane product is not directly shown to be secreted. Supporting Evidence: PMID:19467631 Fluorescence microscopy revealed that the protein was located primarily in the ER. PMID:19467631 C42 in the transmembrane domain and C447 in the exoplasmic domain |
| GO:0005737 cytoplasm | IDA PMID:19467631 The single NTPase gene of Drosophila melanogaster encodes an... | KEEP AS NON CORE | Summary: Cytoplasm is a broad location compatible with the ER compartment. Reason: The primary localization is ER-associated rather than freely cytosolic. Cytoplasm includes extranuclear organelles, so this term is broad rather than evidence for a soluble cytosolic enzyme. Supporting Evidence: PMID:19467631 Fluorescence microscopy revealed that the protein was located primarily in the ER. |
| GO:0005794 Golgi apparatus | IEA GO_REF:0000117 | UNDECIDED | Summary: Golgi residence requires isoform- and compartment-specific support. Reason: The accessible direct microscopy identifies predominantly ER-localized protein. A possible Golgi pool is not refuted, but glycoprotein-processing function alone does not demonstrate Golgi residence. Supporting Evidence: PMID:19467631 Fluorescence microscopy revealed that the protein was located primarily in the ER. |
| GO:0005886 plasma membrane | IEA GO_REF:0000117 | UNDECIDED | Summary: The exact product is not established as a cell-surface ectoenzyme. Reason: Detergent dependence and ER microscopy support an intracellular NTPDase6. Family membership includes surface NTPDases, so surface trafficking should not be assumed for this protein. Supporting Evidence: PMID:19467631 Fluorescence microscopy revealed that the protein was located primarily in the ER. |
| GO:0016787 hydrolase activity | IEA GO_REF:0000002 | MODIFY | Summary: Nucleoside diphosphate hydrolysis specifies the generic hydrolase term. Reason: GDP/UDP/IDP substrate tests support nucleoside diphosphate phosphatase activity rather than an undifferentiated hydrolase label. Proposed replacements: nucleoside diphosphate phosphatase activity Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. |
| GO:0017110 nucleoside diphosphate phosphatase activity | IEA GO_REF:0000003 | ACCEPT | Summary: The enzyme is a nucleoside diphosphate phosphohydrolase. Reason: Direct assays of the cloned fly protein establish GDP, UDP and IDP turnover with poor turnover of other NDPs and NTPs. This supports a diphosphatase interpretation more precisely than the historical apyrase name. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. |
| GO:0036384 CDP phosphatase activity | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: CDP is not a preferred substrate of the characterized enzyme. Reason: The primary substrate comparison identifies GDP, UDP and IDP as efficient substrates and other NDP/NTP as poor substrates. A weak in-vitro side reaction should not be presented as the core physiological specificity. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. |
| GO:0045134 UDP phosphatase activity | IDA PMID:19467631 The single NTPase gene of Drosophila melanogaster encodes an... | ACCEPT | Summary: UDP hydrolysis is directly demonstrated. Reason: UDPase activity is unmasked by detergent in transfected S2 cells, consistent with an intracellular membrane enzyme whose catalytic domain faces the secretory-pathway lumen. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. PMID:19467631 Fluorescence microscopy revealed that the protein was located primarily in the ER. |
| GO:0045134 UDP phosphatase activity | IEA GO_REF:0000117 | ACCEPT | Summary: UDP hydrolysis is directly demonstrated. Reason: UDPase activity is unmasked by detergent in transfected S2 cells, consistent with an intracellular membrane enzyme whose catalytic domain faces the secretory-pathway lumen. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. PMID:19467631 Fluorescence microscopy revealed that the protein was located primarily in the ER. |
| GO:1990003 IDP phosphatase activity | IEA GO_REF:0000117 | ACCEPT | Summary: IDP hydrolysis is supported by direct substrate comparison. Reason: The enzyme hydrolyzes IDP as well as GDP and UDP, making the IDP term correct despite its electronic provenance. Supporting Evidence: PMID:19467631 The enzyme hydrolyzed UDP, GDP, and IDP equally well whereas other NDP and NTP were poor substrates. |
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