GSS

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0043295 glutathione binding	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for glutathione binding supported by phylogenetic analysis. Crystal structure of human GSS (PMID:10369661) demonstrates direct binding of glutathione as a product of the reaction, confirming this molecular function. Reason: Glutathione binding is a core function of GSS as the enzyme binds its product glutathione. The crystal structure at 2.1 A resolution shows GSS in complex with ADP, magnesium ions, and glutathione (PMID:10369661). This IBA annotation is consistent with experimental IDA evidence. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event. file:human/GSS/GSS-deep-research-falcon.md model: Edison Scientific Literature
GO:0005829 cytosol	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for cytosol localization based on phylogenetic analysis. GSH biosynthesis is known to occur in the cytosol where the biosynthetic enzymes GCL and GSS operate. Reason: Cytosolic localization is the established site of de novo GSH synthesis. Multiple lines of evidence including Reactome pathway data and biochemical studies confirm that GSS functions in the cytosol. This is consistent with the known pathway where GSH is synthesized in the cytosol and then distributed to other organelles. Supporting Evidence: DOI:10.3390/antiox12111953
GO:0004363 glutathione synthase activity	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for glutathione synthase activity (EC 6.3.2.3). This is the defining enzymatic function of GSS, catalyzing gamma-glutamyl-cysteine + glycine + ATP to form glutathione + ADP + Pi. Reason: This is the core molecular function of GSS. The enzyme activity was experimentally demonstrated with recombinant human GSS showing specific activity of 1.73 micromol/min per mg protein (PMID:7646467). The annotation is well-supported by phylogenetic conservation and multiple experimental studies. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase. file:human/GSS/GSS-deep-research-falcon.md
GO:0000166 nucleotide binding	IEA GO_REF:0000043	ACCEPT	Summary: IEA annotation for nucleotide binding based on UniProtKB keyword mapping. GSS binds ATP as a substrate for the ligation reaction. Reason: While this is a broad term, it is accurate. GSS is an ATP-dependent ligase and binds ATP during catalysis. The more specific term GO:0005524 (ATP binding) is also annotated with IDA evidence (PMID:10369661). This IEA annotation provides valid coverage at a broader level. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0004363 glutathione synthase activity	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for glutathione synthase activity based on combined automated methods including InterPro domain mapping and EC number assignment. Reason: Duplicate annotation with different evidence type. The annotation is correct as this is the core enzymatic function. Multiple evidence types supporting the same annotation is appropriate. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase.
GO:0005524 ATP binding	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for ATP binding based on InterPro domain mapping and keyword mapping. GSS uses ATP as a co-substrate for the ligation reaction. Reason: ATP binding is essential for GSS catalysis. This IEA annotation is consistent with IDA evidence from PMID:10369661 showing ADP in the crystal structure. Both GCL and GSS are ATP-dependent with low micromolar Km values for ATP. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0006750 glutathione biosynthetic process	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for glutathione biosynthetic process. GSS catalyzes the second and final step in the two-step pathway of glutathione biosynthesis. Reason: This is a core biological process for GSS. The enzyme is part of the two-step GSH biosynthesis pathway where GCL catalyzes step 1 (formation of gamma-glutamyl-cysteine) and GSS catalyzes step 2 (addition of glycine to form glutathione). This annotation accurately captures the biological process in which GSS participates. Supporting Evidence: PMID:8896573 Mutations in the glutathione synthetase gene cause 5-oxoprolinuria. file:human/GSS/GSS-deep-research-falcon.md
GO:0016874 ligase activity	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for ligase activity based on InterPro domain mapping and keyword mapping. GSS is classified as EC 6.3.2.3, a carbon-nitrogen ligase. Reason: GSS is indeed a ligase that joins gamma-glutamyl-cysteine and glycine with ATP hydrolysis. The crystal structure confirms GSS belongs to the ATP-grasp superfamily of ligases (PMID:10369661). While more specific terms exist, this parent term is accurate. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0046872 metal ion binding	IEA GO_REF:0000043	ACCEPT	Summary: IEA annotation for metal ion binding based on UniProtKB keyword mapping. GSS requires magnesium ions for catalysis. Reason: While broad, this annotation is accurate. GSS binds magnesium ions as an essential cofactor. The crystal structure shows two Mg2+ ions per subunit (PMID:10369661). The more specific term GO:0000287 (magnesium ion binding) is also annotated with IDA evidence. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0005515 protein binding	IPI PMID:21044950 Genome-wide YFP fluorescence complementation screen identifi...	REMOVE	Summary: IPI annotation for protein binding based on interaction with TERF1 detected in a high-throughput YFP fluorescence complementation screen for telomere signaling regulators. Reason: This annotation to the generic term 'protein binding' provides little functional insight. The interaction with TERF1 (telomeric repeat binding factor 1) detected in a high-throughput screen is not validated by targeted experiments and has unclear biological significance. GSS is a metabolic enzyme with no established role in telomere biology. The UniProt interaction database lists this with only 2 experiments. This likely represents a non-specific or artifactual interaction. Supporting Evidence: PMID:21044950 Epub 2010 Nov 2. Genome-wide YFP fluorescence complementation screen identifies new regulators for telomere signaling in human cells.
GO:0042802 identical protein binding	IPI PMID:21988832 Toward an understanding of the protein interaction network o...	ACCEPT	Summary: IPI annotation for identical protein binding from a large-scale proteomics study of the human liver interactome. Reason: GSS functions as a homodimer, so identical protein binding is a valid annotation. Multiple lines of evidence support homodimerization including crystal structure (PMID:10369661), biochemical characterization (PMID:7646467), and proteomics studies. The homodimeric nature is functionally relevant for catalysis. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase. PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event. PMID:21988832 Toward an understanding of the protein interaction network of the human liver.
GO:0042802 identical protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	ACCEPT	Summary: IPI annotation for identical protein binding from a proteome-scale map of the human interactome network. Reason: Duplicate annotation with different evidence source. GSS homodimerization is well-established and functionally relevant for the enzyme. Multiple independent studies detecting this interaction strengthens confidence. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase. PMID:25416956 A proteome-scale map of the human interactome network.
GO:0042802 identical protein binding	IPI PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by ...	ACCEPT	Summary: IPI annotation for identical protein binding from a study on protein interaction capabilities affected by alternative splicing. Reason: Duplicate annotation with different evidence source. The homodimeric nature of GSS is well-established across multiple studies and is essential for enzymatic function. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase. PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by Alternative Splicing.
GO:0042802 identical protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	ACCEPT	Summary: IPI annotation for identical protein binding from a reference map of the human binary protein interactome. Reason: Duplicate annotation with different evidence source. Multiple independent high-throughput studies and structural data consistently show GSS homodimerization, providing strong confidence in this annotation. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase. PMID:32296183 Apr 8. A reference map of the human binary protein interactome.
GO:0005654 nucleoplasm	IDA GO_REF:0000052	KEEP AS NON CORE	Summary: IDA annotation for nucleoplasm localization based on immunofluorescence data curation from the Human Protein Atlas. Reason: While the primary site of GSH biosynthesis is the cytosol, detection in the nucleoplasm by immunofluorescence may reflect GSS shuttling or secondary localization. This is not inconsistent with the known biology as GSH is required in the nucleus for redox regulation and transcription factor function. However, the primary functional location remains the cytosol. Supporting Evidence: DOI:10.3390/antiox12111953
GO:0070062 extracellular exosome	HDA PMID:23533145 In-depth proteomic analyses of exosomes isolated from expres...	KEEP AS NON CORE	Summary: HDA annotation for extracellular exosome localization from proteomics analysis of exosomes isolated from prostatic secretions in urine. Reason: Detection in exosomes represents a secondary localization rather than the primary functional compartment. Many cytosolic proteins are found in exosomes as part of general cellular content packaging. This does not reflect the core function or localization of GSS. Supporting Evidence: PMID:23533145 2013 Apr 23. In-depth proteomic analyses of exosomes isolated from expressed prostatic secretions in urine.
GO:0005829 cytosol	TAS Reactome:R-HSA-5602901	ACCEPT	Summary: TAS annotation for cytosol localization from Reactome pathway annotation for the defective GSS pathway. Reason: Cytosol is the established primary location for GSH biosynthesis. This Reactome annotation is consistent with the known biochemistry and other evidence sources including IBA phylogenetic data. Supporting Evidence: DOI:10.3390/antiox12111953
GO:0070062 extracellular exosome	HDA PMID:19056867 Large-scale proteomics and phosphoproteomics of urinary exos...	KEEP AS NON CORE	Summary: HDA annotation for extracellular exosome from large-scale proteomics and phosphoproteomics of urinary exosomes. Reason: Duplicate annotation with different evidence source. Detection in exosomes is a secondary localization not reflecting the primary functional site. Supporting Evidence: PMID:19056867 2008 Dec 3. Large-scale proteomics and phosphoproteomics of urinary exosomes.
GO:0005829 cytosol	TAS Reactome:R-HSA-174394	ACCEPT	Summary: TAS annotation for cytosol localization from Reactome pathway annotation for GSH synthesis. Reason: Duplicate annotation with different evidence source. Cytosolic localization is well-established as the site of de novo glutathione biosynthesis. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase.
GO:0000287 magnesium ion binding	IDA PMID:10369661 Molecular basis of glutathione synthetase deficiency and a r...	ACCEPT	Summary: IDA annotation for magnesium ion binding from crystal structure determination showing two Mg2+ ions bound per subunit. Reason: Magnesium is an essential cofactor for GSS catalysis. The crystal structure at 2.1 A resolution clearly shows two magnesium ions per subunit, and UniProt notes 1 Mg2+ ion per subunit for the cofactor annotation. This is a core molecular function annotation. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0005524 ATP binding	IDA PMID:10369661 Molecular basis of glutathione synthetase deficiency and a r...	ACCEPT	Summary: IDA annotation for ATP binding from crystal structure showing ADP bound in the active site. Reason: ATP binding is essential for GSS catalysis as the enzyme is an ATP-dependent ligase. The crystal structure shows ADP (product of ATP hydrolysis) in the active site. This is a core molecular function for the enzyme. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0042803 protein homodimerization activity	IDA PMID:10369661 Molecular basis of glutathione synthetase deficiency and a r...	ACCEPT	Summary: IDA annotation for protein homodimerization activity from crystal structure and biochemical characterization showing GSS functions as a homodimer. Reason: GSS functions as a homodimer. The crystal structure confirms the dimeric arrangement, and biochemical studies (PMID:7646467) demonstrated the recombinant protein occurs as a homodimer. Homodimerization is essential for enzyme function and represents a core molecular activity. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase. PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0043295 glutathione binding	IDA PMID:10369661 Molecular basis of glutathione synthetase deficiency and a r...	ACCEPT	Summary: IDA annotation for glutathione binding from crystal structure showing glutathione bound in the active site. Reason: The crystal structure directly demonstrates glutathione bound in the active site. Glutathione is the product of the reaction catalyzed by GSS, and product binding is integral to the catalytic mechanism. This is a core molecular function. Supporting Evidence: PMID:10369661 Molecular basis of glutathione synthetase deficiency and a rare gene permutation event.
GO:0004363 glutathione synthase activity	TAS PMID:7646467 Sequencing and expression of a cDNA for human glutathione sy...	ACCEPT	Summary: TAS annotation for glutathione synthase activity based on the original cloning and expression study of human GSS demonstrating enzymatic activity. Reason: This is the defining enzymatic activity of GSS. The study cloned human GSS cDNA, expressed it in E. coli, purified the recombinant enzyme, and demonstrated glutathione synthase activity with specific activity of 1.73 micromol/min per mg. This represents primary experimental evidence for the core function. Supporting Evidence: PMID:7646467 Sequencing and expression of a cDNA for human glutathione synthetase.
GO:0006520 amino acid metabolic process	TAS PMID:8896573 Mutations in the glutathione synthetase gene cause 5-oxoprol...	MODIFY	Summary: TAS annotation for amino acid metabolic process. GSS participates in glutathione metabolism which involves amino acid substrates glycine, cysteine, and glutamate. Reason: While technically accurate as GSH biosynthesis involves amino acid metabolism, this is an overly broad annotation. The more specific term GO:0006750 (glutathione biosynthetic process) better captures the biological process in which GSS participates. The amino acid metabolic process annotation does not add information beyond what is captured by the more specific term. Proposed replacements: glutathione biosynthetic process Supporting Evidence: PMID:8896573 Mutations in the glutathione synthetase gene cause 5-oxoprolinuria.
GO:0006979 response to oxidative stress	TAS PMID:465367 Oxidative damage to neutrophils in glutathione synthetase de...	KEEP AS NON CORE	Summary: TAS annotation for response to oxidative stress based on a study of oxidative damage in neutrophils from GSS-deficient patients. Reason: The referenced study (PMID:465367) examines the consequences of GSS deficiency on neutrophil function under oxidative stress. The study shows that GSH-deficient cells have impaired protection against peroxide generated during phagocytosis. However, this reflects the downstream consequence of GSH deficiency rather than a direct role of GSS in stress response signaling. GSS produces GSH which then provides antioxidant protection, but GSS itself does not directly respond to or sense oxidative stress. This annotation is not wrong but represents an indirect relationship. Supporting Evidence: PMID:465367 Oxidative damage to neutrophils in glutathione synthetase deficiency.
GO:0007399 nervous system development	TAS PMID:8896573 Mutations in the glutathione synthetase gene cause 5-oxoprol...	KEEP AS NON CORE	Summary: TAS annotation for nervous system development based on neurological dysfunction observed in severe GSS deficiency patients. Reason: The referenced study describes neurological dysfunction in severe GSS deficiency cases, indicating the importance of adequate GSH for nervous system development/function. However, this reflects the phenotypic consequences of GSS deficiency rather than a direct molecular role in nervous system development. GSS produces GSH which is required for general cellular antioxidant protection including in neurons, but GSS is not a specific developmental regulator. This is an indirect annotation based on disease phenotype rather than direct molecular function. Supporting Evidence: PMID:8896573 Mutations in the glutathione synthetase gene cause 5-oxoprolinuria.

Gene Description

Existing Annotations Review

Core Functions

References

Tags

Deep Research

Falcon

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