GOT1 (Glutamic-Oxaloacetic Transaminase 1), also known as Aspartate Aminotransferase 1 (AST1), cAST (cytosolic aspartate aminotransferase), or AAT1, encodes a crucial metabolic enzyme that catalyzes the reversible transamination between aspartate and α-ketoglutarate, producing glutamate and oxaloacetate. Located on chromosome 10q24.3, GOT1 plays essential roles in amino acid metabolism, the malate-aspartate shuttle, and neuronal energy metabolism. The enzyme is critical for maintaining glutamate and aspartate homeostasis in the brain and has been implicated in Alzheimer's disease, Parkinson's disease, and various metabolic and neurodegenerative conditions.
| Attribute |
Value |
| Gene Symbol |
GOT1 |
| Full Name |
Glutamic-Oxaloacetic Transaminase 1 |
| Alternative Names |
AST1, cAST, AAT1, Aspartate Aminotransferase 1 |
| Chromosomal Location |
10q24.3 |
| NCBI Gene ID |
2805 |
| Ensembl ID |
ENSG00000163283 |
| UniProt ID |
P17174 |
| OMIM |
138150 |
| Protein Class |
Enzyme; Aminotransferase |
| Associated Diseases |
Alzheimer's disease, Parkinson's disease, metabolic disorders |
The GOT1 gene spans approximately 14 kb and consists of 11 exons encoding a 413-amino acid protein. The gene is widely expressed with highest levels in heart, liver, and brain. Alternative splicing generates multiple mRNA variants with tissue-specific expression patterns.
GOT1 is a homodimeric enzyme:
- Subunit size — 413 amino acids per monomer (~45 kDa)
- Quaternary structure — Active as homodimer (90 kDa)
- Pyridoxal phosphate — Contains vitamin B6 cofactor at Lys258
- PLP binding — Pyridoxal 5'-phosphate forms Schiff base with Lys258
- Substrate binding — Distinct sites for aspartate and α-ketoglutarate
- Catalytic mechanism — Ping-pong bi-bi transamination
| Property |
GOT1 (cAST) |
GOT2 (mAST) |
| Location |
Cytosol |
Mitochondria |
| Gene |
GOT1 |
GOT2 |
| Isoform length |
413 aa |
430 aa |
| Tissue distribution |
Broad |
High in heart, liver, brain |
| pI |
5.4 |
9.0 |
GOT1 catalyzes the reversible transamination reaction:
L-Aspartate + α-Ketoglutarate ↔ Oxaloacetate + L-Glutamate
This reaction is central to multiple metabolic pathways:
- Amino acid metabolism — Interconversion of aspartate and glutamate
- Gluconeogenesis — Oxaloacetate is a key gluconeogenic intermediate
- Urea cycle — Aspartate donates nitrogen for urea synthesis
- Malate-aspartate shuttle — Transfers reducing equivalents across mitochondrial membrane
The malate-aspartate shuttle is the primary mechanism for transferring reducing equivalents (NADH) from cytosol to mitochondria in the brain:
- Cytosolic GOT1 converts oxaloacetate + glutamate → aspartate + α-ketoglutarate
- Aspartate is transported into mitochondria via the aspartate-glutamate carrier (AGC)
- Mitochondrial GOT2 converts aspartate + α-ketoglutarate → oxaloacetate + glutamate
- Malate dehydrogenase converts oxaloacetate + NADH → malate + NAD⁺
- Malate enters mitochondria via malate-α-ketoglutarate carrier
- Mitochondrial malate is converted back to oxaloacetate, generating NADH for oxidative phosphorylation
This shuttle is particularly important in neurons, which rely heavily on oxidative phosphorylation for energy. Unlike glycolysis, oxidative phosphorylation requires the malate-aspartate shuttle to transport electrons into the mitochondria.
GOT1 is essential for glutamate-glutamine cycle:
- Glutamate uptake — Astrocytes take up synaptic glutamate
- Glutamine formation — Glutamate converted to glutamine by glutamine synthetase
- Glutamine release — Released to neurons
- GOT1 regeneration — Neuronal GOT1 converts glutamine back to glutamate
- TCA cycle anaplerosis — Provides oxaloacetate for citrate synthesis
- Amino acid biosynthesis — Supports protein synthesis
- Gluconeogenesis — Contributes to glucose generation in liver/kidney
GOT1 is expressed throughout the brain with high activity in metabolically active regions:
| Region |
Expression Level |
Cell Types |
| Cerebral cortex |
Very high |
Pyramidal neurons, interneurons |
| Hippocampus |
Very high |
CA1-CA3 pyramidal cells, granule cells |
| Cerebellum |
High |
Purkinje cells, granule cells |
| Basal ganglia |
High |
Medium spiny neurons, dopaminergic terminals |
| Brainstem |
Moderate |
Various neuron types |
| Thalamus |
Moderate |
Relay neurons |
Within the brain, GOT1 is expressed in both neurons and astrocytes:
- Neuronal GOT1 — Primarily cytosolic, supports neurotransmitter synthesis
- Astrocytic GOT1 — Critical for glutamate recycling and metabolic coupling
- Cytosolic localization — Predominantly in cytosol
- Mitochondrial association — Partial mitochondrial localization in some cells
- Synaptic terminals — Present in presynaptic terminals for neurotransmitter recycling
GOT1 activity is tightly regulated:
- Hormonal control — Glucocorticoids increase GOT1 expression
- Nutritional state — Fasting alters hepatic GOT1
- Developmental expression — High in developing brain
- Product inhibition — Glutamate and oxaloacetate inhibit activity
- Substrate activation — Aspartate and α-ketoglutarate activate
- PLP availability — Requires pyridoxal phosphate
- Phosphorylation — Some regulatory serine/threonine sites
- Acetylation — Lysine acetylation affects activity
- Proteolytic cleavage — Generated in certain stress conditions
GOT1 alterations have been extensively documented in Alzheimer's disease. Multiple studies have shown that GOT activity is significantly reduced in AD brain tissue, with reported decreases of 30-50% compared to age-matched controls[@hassen2021]. This reduction is particularly pronounced in the hippocampus and cerebral cortex, regions most affected by AD pathology[@cunnane2020].
The metabolic dysfunction in AD involves several interconnected mechanisms that converge on GOT1 function:
- Reduced GOT activity — 30-50% reduction in AD brain tissue[@a1988]
- Altered aspartate-glutamate metabolism — Affects neurotransmitter pools and excitability
- Impaired malate-aspartate shuttle — Contributes to mitochondrial dysfunction[@mehrabi2022]
- Energy metabolism deficits — ATP production impaired in AD neurons due to reduced NADH shuttling
- Excitotoxicity — Glutamate dysregulation contributes to neuronal death through NMDA receptor overactivation
- Tau pathology interactions — Metabolic dysfunction exacerbates tau-induced damage
The malate-aspartate shuttle is particularly vulnerable in AD because neurons rely almost exclusively on oxidative phosphorylation, unlike astrocytes which can switch to glycolysis[@pellerin2008]. When GOT1 activity is reduced, the shuttle cannot efficiently transfer NADH from cytosol to mitochondria, leading to a critical energy deficit that compounds the already-impaired mitochondrial function in AD[@cunnane2020].
GOT1 is relevant to Parkinson's disease through its role in dopaminergic neuron metabolism and mitochondrial function[@gandhi2020]. The substantia nigra pars compacta, which degenerates in PD, has particularly high metabolic demands that make it vulnerable to GOT1 dysfunction:
- Altered transaminase activities — Reduced in substantia nigra and striatum[@jager2000]
- Mitochondrial dysfunction — Impaired NADH shuttle function compounds complex I deficiency
- Excitotoxicity — Glutamate metabolism alterations may contribute to dopaminergic neuron death
- Energy crisis — Complex I deficiency affects malate-aspartate shuttle efficiency
Dopaminergic neurons have uniquely high energy requirements due to their pacemaking activity, which continuously demands ATP for ionic gradient maintenance. The GOT1-mediated malate-aspartate shuttle is essential for meeting these demands, and any impairment can lead to neuronal dysfunction and death[@gandhi2020].
- Motor neuron metabolism — GOT1 alterations in spinal cord
- Excitotoxic mechanisms — Glutamate homeostasis disrupted
- Astrocyte dysfunction — Impaired metabolic coupling
- Non-alcoholic fatty liver disease — GOT1 elevated as marker
- Cardiovascular disease — Metabolic syndrome affects brain GOT1
- Diabetes — Altered glycemic control affects neuronal metabolism
¶ Research and Clinical Evidence
Post-mortem studies have consistently shown GOT1 alterations in neurodegenerative diseases:
| Study |
Finding |
PMID |
| Hassen et al. 2021 |
Metabolic dysfunction in AD brain |
34588934 |
| Cunnane et al. 2020 |
Brain energy metabolism in AD |
31830586 |
| Mehrabi et al. 2022 |
Astrocyte metabolic dysfunction |
35633412 |
| Gandhi et al. 2020 |
Metabolic alterations in PD |
32804087 |
| Kumar et al. 2023 |
Astrocyte-neuron coupling |
37213456 |
Serum and CSF GOT levels show promise as biomarkers for neurodegenerative disease progression[@pal2016]. Elevated serum GOT1 is associated with:
- Disease severity in AD and PD
- Cognitive decline trajectory
- Motor symptom progression in PD
Current research is exploring several strategies targeting GOT1 and malate-aspartate shuttle function[@daniele2014]:
- Metabolic enhancers — Compounds that boost shuttle activity
- Cofactor supplementation — Alpha-ketoglutarate and pyridoxal phosphate
- Astrocyte-targeted therapies — Restore metabolic coupling
- Mitochondrial protectants — Preserve shuttle function
GOT1 supports neuronal energy through:
- NADH transport — Shuttles electrons into mitochondria
- ATP production — Supports oxidative phosphorylation
- Metabolic flexibility — Enables alternative substrate utilization
- Anaplerosis — Maintains TCA cycle intermediates
The glutamate-glutamine cycle depends on GOT1:
- Synaptic glutamate release — Vesicular release during neurotransmission
- Astrocyte uptake — EAAT1/EAAT2 transport glutamate
- GOT1 conversion — Glutamate → glutamine via GS
- Neuronal uptake — Glutamine transported to neurons
- GOT1 regeneration — Glutamine → glutamate in neurons
GOT1 affects cellular redox status:
- NAD⁺/NADH ratio — Shuttle activity maintains redox balance
- Antioxidant support — Supports glutathione synthesis
- Mitochondrial function — Electron transport chain support
GOT1 is a potential therapeutic target:
- Enhancing malate-aspartate shuttle — Improve neuronal energy
- Boosting astrocyte-neuron metabolic coupling — Restore metabolic support
- Protecting against oxidative stress — NAD⁺/NADH ratio maintenance
- Serum GOT levels — Biomarker for neurodegenerative disease progression
- CSF GOT activity — Diagnostic marker for AD and PD
- GOT1 polymorphisms — Genetic risk modifiers
- Small molecule activators — Enhance GOT1 activity
- Modulators of malate-aspartate shuttle — Target metabolic coupling
- Cofactor supplementation — Alpha-ketoglutarate as neuroprotective strategy
| Interactor |
Interaction Type |
Function |
| GOT2 |
Isozyme partner |
Malate-aspartate shuttle |
| Glutamine synthetase |
Enzyme coupling |
Glutamate-glutamine cycle |
| EAAT1/2 |
Transport coupling |
Glutamate uptake |
| MDH1/2 |
Pathway coupling |
Malate conversion |
| AGC1/2 (citrin) |
Transporter |
Mitochondrial aspartate transport |
- Reich E, Glutamate-oxaloacetate transaminase (GOT) (1973)
- Sak K et al, Aspartate aminotransferase isoenzymes in mammalian tissues (2019)
- Bkelser AH et al, The malate-aspartate shuttle in brain mitochondria (1982)
- Belanger M et al, Brain energy metabolism: roles of astrocytes and neurons (2008)
- Pellerin L et al, Astrocyte-neuron metabolic coupling (2008)
- Schousboe A et al, Amino acid neurotransmitters: from extracellular space to metabolism (2001)
- A et al, Alterations of transaminases in Alzheimer's disease brain (1988)
- Jager W et al, Metabolic alterations in Parkinson's disease brain (2000)
- Kimelberg HK, Glutamate uptake and excitotoxicity (2009)
- Daniele S et al, Metabolic modulation in neurodegenerative diseases (2014)
- Pal R et al, Serum transaminases as biomarkers in neurodegeneration (2016)
- Hassen G et al, Metabolic dysfunction in Alzheimer's disease (2021)
- Mehrabi S et al, Astrocyte metabolic dysfunction in neurodegenerative diseases (2022)
- Gandhi S et al, Metabolic alterations in Parkinson's disease (2020)
- Cunnane SC et al, Brain energy metabolism in Alzheimer's disease (2020)
- Kumar A et al, Targeting astrocyte-neuron metabolic coupling (2023)