Component

Glutamate decarboxylase 65 / GAD2

Glutamate decarboxylase 65 / GAD2. Species, exposure and limitations are retained in each linked claim.

4 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What it acts on

  1. The brain contains two forms of the GABA synthetic enzyme glutamate decarboxylase which differ in molecular size, amino acid sequence, antigenicity, cellular and subcellular location, and interaction with the GAD cofactor pyridoxal phosphate, these forms GAD65 and GAD67 derive from two genes, and their distinctive properties provide a substrate for understanding not only the multiple roles of GABA in the nervous system but also the autoimmune response to GAD in insulin-dependent diabetes mellitus.

    Glutamate decarboxylase 65 / GAD2 → Glutamate decarboxylase 67 / GAD1 source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/gaba-research/2069816.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "4d940e6978ff77eeee89607aa24fde9036bb58d013063463389a1ca0cb0eb080", "start_char": 0, "end_char": 738, "text_sha256": "4d940e6978ff77eeee89607aa24fde9036bb58d013063463389a1ca0cb0eb080"}
    experimental_model
    Molecular and immunological comparison of the two brain forms of the GABA synthetic enzyme
    exposure
    The two glutamate decarboxylase forms compared for size, sequence, antigenicity, location and cofactor interaction
    limitations
    A characterisation of two gene products. The pancreatic and autoimmune connections are stated as context rather than measured here.
    nutrient_topic
    GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. · Gamma-aminobutyric acid
    organism
    Rat and human genes
    plain_language
    There are two versions of the enzyme that makes this transmitter, and they differ in where they sit and how tightly they hold their cofactor.
    primary_references
    [gb-p2069816] Two genes encode distinct glutamate decarboxylases. (1991). https://pubmed.ncbi.nlm.nih.gov/2069816/ DOI: 10.1016/0896-6273(91)90077-d
    tissue_or_cell_type
    Brain and pancreas

    GABA: a ligand with no sign of its own, the cofactor that limits its synthesis, the barrier that keeps it out of the brain, and the immune settings where the same molecule protects and harms (2026-09-22) · lines 92–103

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Molecular and immunological comparison of the two brain forms of the GABA synthetic enzyme · source_derived_draft · unverified_draft

    ### gb-two-enzymes-not-one The brain contains two forms of the GABA synthetic enzyme glutamate decarboxylase which differ in molecular size, amino acid sequence, antigenicity, cellular and subcellular location, and interaction with the GAD cofactor pyridoxal phosphate, these forms GAD65 and GAD67 derive from two genes, and their distinctive properties provide a substrate for understanding not only the multiple roles of GABA in the nervous system but also the autoimmune response to GAD in insulin-dependent diabetes mellitus. Condition category: normal nutrient_topic: GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. plain_language: There are two versions of the enzyme that makes this transmitter, and they differ in where they sit and how tightly they hold their cofactor. organism: Rat and human genes tissue_or_cell_type: Brain and pancreas experimental_model: Molecular and immunological comparison of the two brain forms of the GABA synthetic enzyme limitations: A characterisation of two gene products. The pancreatic and autoimmune connections are stated as context rather than measured here. exposure: The two glutamate decarboxylase forms compared for size, sequence, antigenicity, location and cofactor interaction evidence_span: {"source_cache": "artifacts/gaba-research/2069816.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "4d940e6978ff77eeee89607aa24fde9036bb58d013063463389a1ca0cb0eb080", "start_char": 0, "end_char": 738, "text_sha256": "4d940e6978ff77eeee89607aa24fde9036bb58d013063463389a1ca0cb0eb080"} [gb-p2069816] Two genes encode distinct glutamate decarboxylases. (1991). https://pubmed.ncbi.nlm.nih.gov/2069816/ DOI: 10.1016/0896-6273(91)90077-d
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Only GAD65 acts as a major autoantigen, frequently implicated in type 1 diabetes and other autoimmune diseases, hydrogen-deuterium exchange reveals local dynamics accompanying autoinactivation with the catalytic loop promoting collective motions at the C-terminal domain and pyridoxal-5-phosphate domain interface, in the complex with the autoantibody the heavy chain complementarity-determining regions dominate the interaction with a long CDRH3 bridging the GAD65 dimer, and thus intrinsic dynamics rather than sequence differences within epitopes appear to be responsible for the contrasting autoantigenicities of GAD65 and GAD67.

    Conformational dynamics of GAD65 → Autoantigenicity of GAD65 source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/gaba-research/40055307.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "832b0c18514e12230379ef877a5bd017fc67e23d762d3b9f00f5d59dc2f7efe2", "start_char": 0, "end_char": 1448, "text_sha256": "832b0c18514e12230379ef877a5bd017fc67e23d762d3b9f00f5d59dc2f7efe2"}
    experimental_model
    Hydrogen-deuterium exchange mass spectrometry, X-ray crystallography and cryo-electron microscopy of the enzyme with a human autoantibody
    exposure
    Apo and holo forms of GAD65 and the complex with the autoantibody b96.11
    limitations
    Structural and dynamic work on isolated protein. The conclusion about autoantigenicity is an interpretation of dynamics rather than an immunological measurement.
    nutrient_topic
    GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. · Gamma-aminobutyric acid
    organism
    Human protein
    plain_language
    What makes one of the two enzymes the target of an autoimmune attack is how much it moves, not how its surface reads.
    primary_references
    [gb-p40055307] Structure and dynamics of GAD65 in complex with an autoimmune polyendocrine syndrome type 2-associated autoantibody. (2025). https://pubmed.ncbi.nlm.nih.gov/40055307/ DOI: 10.1038/s41467-025-57492-4
    tissue_or_cell_type
    Recombinant enzyme

    GABA: a ligand with no sign of its own, the cofactor that limits its synthesis, the barrier that keeps it out of the brain, and the immune settings where the same molecule protects and harms (2026-09-22) · lines 144–155

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Hydrogen-deuterium exchange mass spectrometry, X-ray crystallography and cryo-electron microscopy of the enzyme with a human autoantibody · source_derived_draft · unverified_draft

    ### gb-dynamics-not-sequence-make-the-autoantigen Only GAD65 acts as a major autoantigen, frequently implicated in type 1 diabetes and other autoimmune diseases, hydrogen-deuterium exchange reveals local dynamics accompanying autoinactivation with the catalytic loop promoting collective motions at the C-terminal domain and pyridoxal-5-phosphate domain interface, in the complex with the autoantibody the heavy chain complementarity-determining regions dominate the interaction with a long CDRH3 bridging the GAD65 dimer, and thus intrinsic dynamics rather than sequence differences within epitopes appear to be responsible for the contrasting autoantigenicities of GAD65 and GAD67. Condition category: normal nutrient_topic: GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. plain_language: What makes one of the two enzymes the target of an autoimmune attack is how much it moves, not how its surface reads. organism: Human protein tissue_or_cell_type: Recombinant enzyme experimental_model: Hydrogen-deuterium exchange mass spectrometry, X-ray crystallography and cryo-electron microscopy of the enzyme with a human autoantibody limitations: Structural and dynamic work on isolated protein. The conclusion about autoantigenicity is an interpretation of dynamics rather than an immunological measurement. exposure: Apo and holo forms of GAD65 and the complex with the autoantibody b96.11 evidence_span: {"source_cache": "artifacts/gaba-research/40055307.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "832b0c18514e12230379ef877a5bd017fc67e23d762d3b9f00f5d59dc2f7efe2", "start_char": 0, "end_char": 1448, "text_sha256": "832b0c18514e12230379ef877a5bd017fc67e23d762d3b9f00f5d59dc2f7efe2"} [gb-p40055307] Structure and dynamics of GAD65 in complex with an autoimmune polyendocrine syndrome type 2-associated autoantibody. (2025). https://pubmed.ncbi.nlm.nih.gov/40055307/ DOI: 10.1038/s41467-025-57492-4
    Complete structured claim and evidence

  2. At least 50% of glutamate decarboxylase is present in brain as apoenzyme, that is enzyme without bound cofactor, which serves as a reservoir of inactive enzyme that can be drawn on when additional GABA synthesis is needed, a substantial majority of the apoenzyme in brain is accounted for by GAD65 although GAD67 also contributes, the interaction of the enzyme with pyridoxal 5-phosphate is a major factor in the short-term regulation of its activity, and the apparent localization of GAD65 in nerve terminals together with the large reserve of apo-GAD65 suggest that GAD65 is specialized to respond to short-term changes in demand for transmitter GABA.

    Apo-glutamate decarboxylase, the form without bound cofactor → Synthesis of GABA from glutamate source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/gaba-research/8419527.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0de2df4de7da887745f27b7c4593a75590b6de3649a2b5b35a1d36980a86b755", "start_char": 0, "end_char": 1425, "text_sha256": "0de2df4de7da887745f27b7c4593a75590b6de3649a2b5b35a1d36980a86b755"}
    experimental_model
    Review of the compartments and short-term regulation of brain GABA synthesis
    exposure
    Glutamate decarboxylase measured as apoenzyme and holoenzyme across brain regions
    limitations
    A review of the enzymology. The apoenzyme fraction is given for total glutamate decarboxylase, with GAD65 accounting for a substantial majority of it rather than being separately quantified.
    nutrient_topic
    GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. · Gamma-aminobutyric acid
    organism
    Rat and human
    plain_language
    Half the enzyme is sitting idle without its cofactor, held in reserve for when more transmitter is suddenly needed.
    primary_references
    [gb-p8419527] Regulation of gamma-aminobutyric acid synthesis in the brain. (1993). https://pubmed.ncbi.nlm.nih.gov/8419527/ DOI: 10.1111/j.1471-4159.1993.tb03165.x
    tissue_or_cell_type
    Brain

    GABA: a ligand with no sign of its own, the cofactor that limits its synthesis, the barrier that keeps it out of the brain, and the immune settings where the same molecule protects and harms (2026-09-22) · lines 105–116

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Review of the compartments and short-term regulation of brain GABA synthesis · source_derived_draft · unverified_draft

    ### gb-half-the-enzyme-waits At least 50% of glutamate decarboxylase is present in brain as apoenzyme, that is enzyme without bound cofactor, which serves as a reservoir of inactive enzyme that can be drawn on when additional GABA synthesis is needed, a substantial majority of the apoenzyme in brain is accounted for by GAD65 although GAD67 also contributes, the interaction of the enzyme with pyridoxal 5-phosphate is a major factor in the short-term regulation of its activity, and the apparent localization of GAD65 in nerve terminals together with the large reserve of apo-GAD65 suggest that GAD65 is specialized to respond to short-term changes in demand for transmitter GABA. Condition category: normal nutrient_topic: GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. plain_language: Half the enzyme is sitting idle without its cofactor, held in reserve for when more transmitter is suddenly needed. organism: Rat and human tissue_or_cell_type: Brain experimental_model: Review of the compartments and short-term regulation of brain GABA synthesis limitations: A review of the enzymology. The apoenzyme fraction is given for total glutamate decarboxylase, with GAD65 accounting for a substantial majority of it rather than being separately quantified. exposure: Glutamate decarboxylase measured as apoenzyme and holoenzyme across brain regions evidence_span: {"source_cache": "artifacts/gaba-research/8419527.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "0de2df4de7da887745f27b7c4593a75590b6de3649a2b5b35a1d36980a86b755", "start_char": 0, "end_char": 1425, "text_sha256": "0de2df4de7da887745f27b7c4593a75590b6de3649a2b5b35a1d36980a86b755"} [gb-p8419527] Regulation of gamma-aminobutyric acid synthesis in the brain. (1993). https://pubmed.ncbi.nlm.nih.gov/8419527/ DOI: 10.1111/j.1471-4159.1993.tb03165.x
    Complete structured claim and evidence

  3. We studied 334 patients aged 10 to 20 years with type 1 diabetes, fasting C-peptide levels of more than 0.3 nanograms per millilitre and detectable serum GAD65 autoantibodies, randomly assigned within 3 months after diagnosis to four doses of GAD-alum, two doses followed by two doses of placebo, or four doses of placebo, the stimulated C-peptide level declined to a similar degree in all study groups and the primary outcome at 15 months did not differ significantly between the combined active-drug groups and the placebo group with P = 0.10, and the use of GAD-alum did not affect the insulin dose, glycated haemoglobin level or hypoglycaemia rate.

    Alum-formulated GAD65 antigen therapy → Stimulated serum C-peptide after a mixed-meal tolerance test source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/gaba-research/22296077.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "fc3bf9a083b3179c8573e993fb61f09412eca7890c3ccfb3ba5b8c0fb26acce8", "start_char": 0, "end_char": 1683, "text_sha256": "fc3bf9a083b3179c8573e993fb61f09412eca7890c3ccfb3ba5b8c0fb26acce8"}
    experimental_model
    Randomised placebo-controlled trial of an alum-formulated autoantigen in 334 patients within three months of diagnosis
    exposure
    Four doses of GAD-alum, two doses followed by placebo, or four doses of placebo, in patients aged 10 to 20 with detectable GAD65 autoantibodies
    limitations
    A properly powered randomised trial with stimulated C-peptide as the primary outcome. It tests the autoantigen as a therapy, not GABA.
    nutrient_topic
    GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. · Gamma-aminobutyric acid
    organism
    Human
    plain_language
    Vaccinating against the enzyme the immune system attacks did not slow the loss of insulin production.
    primary_references
    [gb-p22296077] GAD65 antigen therapy in recently diagnosed type 1 diabetes mellitus. (2012). https://pubmed.ncbi.nlm.nih.gov/22296077/ DOI: 10.1056/nejmoa1107096
    tissue_or_cell_type
    Pancreatic beta cell function

    GABA: a ligand with no sign of its own, the cofactor that limits its synthesis, the barrier that keeps it out of the brain, and the immune settings where the same molecule protects and harms (2026-09-22) · lines 456–467

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Randomised placebo-controlled trial of an alum-formulated autoantigen in 334 patients within three months of diagnosis · source_derived_draft · unverified_draft

    ### gb-targeting-the-autoantigen-did-not-work We studied 334 patients aged 10 to 20 years with type 1 diabetes, fasting C-peptide levels of more than 0.3 nanograms per millilitre and detectable serum GAD65 autoantibodies, randomly assigned within 3 months after diagnosis to four doses of GAD-alum, two doses followed by two doses of placebo, or four doses of placebo, the stimulated C-peptide level declined to a similar degree in all study groups and the primary outcome at 15 months did not differ significantly between the combined active-drug groups and the placebo group with P = 0.10, and the use of GAD-alum did not affect the insulin dose, glycated haemoglobin level or hypoglycaemia rate. Condition category: normal nutrient_topic: GABA research collection; topical membership is not evidence of a direct clinical effect, and the sign of a GABA response depends on the chloride gradient of the cell it was measured in. plain_language: Vaccinating against the enzyme the immune system attacks did not slow the loss of insulin production. organism: Human tissue_or_cell_type: Pancreatic beta cell function experimental_model: Randomised placebo-controlled trial of an alum-formulated autoantigen in 334 patients within three months of diagnosis limitations: A properly powered randomised trial with stimulated C-peptide as the primary outcome. It tests the autoantigen as a therapy, not GABA. exposure: Four doses of GAD-alum, two doses followed by placebo, or four doses of placebo, in patients aged 10 to 20 with detectable GAD65 autoantibodies evidence_span: {"source_cache": "artifacts/gaba-research/22296077.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "fc3bf9a083b3179c8573e993fb61f09412eca7890c3ccfb3ba5b8c0fb26acce8", "start_char": 0, "end_char": 1683, "text_sha256": "fc3bf9a083b3179c8573e993fb61f09412eca7890c3ccfb3ba5b8c0fb26acce8"} [gb-p22296077] GAD65 antigen therapy in recently diagnosed type 1 diabetes mellitus. (2012). https://pubmed.ncbi.nlm.nih.gov/22296077/ DOI: 10.1056/nejmoa1107096
    Complete structured claim and evidence

In the sources

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