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COASY
Coenzyme A synthase
COASY encodes an enzyme that catalyses the final steps of coenzyme A production, essential for cellular energy metabolism and lipid synthesis. The COASY gene provides instructions for making coenzyme A synthase, a bifunctional enzyme required to produce coenzyme A (CoA), a molecule central to hundreds of metabolic reactions.
COASY is located on the long (q) arm of chromosome 17, at band 17q21.2. Arm ratio per GRCh38 - banding schematic.
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Overview
COASY encodes coenzyme A synthase, an enzyme that performs the final two steps in the biosynthesis of coenzyme A, a cofactor required for cellular energy production, fatty acid metabolism, and the synthesis of essential biomolecules. The protein combines two distinct enzymatic activities within a single polypeptide chain, converting phosphopantetheine into dephospho-CoA and then into coenzyme A.
Pathogenic variants in COASY inherited in an autosomal recessive pattern result in CoPAN (COASY protein-associated neurodegeneration), a condition characterised by progressive movement disorder and basal ganglia abnormalities visible on brain imaging. The gene is located on chromosome 17 and is clinically significant in the context of childhood-onset neurological conditions.
What the gene does
Coenzyme A synthase catalyses the final two enzymatic steps required to generate coenzyme A from phosphopantetheine. The protein first adds an adenosine monophosphate group to phosphopantetheine through its phosphopantetheine adenylyltransferase activity, producing dephospho-CoA. The second enzymatic domain then phosphorylates dephospho-CoA to yield the final coenzyme A product.
Coenzyme A serves as an essential cofactor for more than 100 different enzymatic reactions throughout cellular metabolism. It participates in the citric acid cycle, fatty acid oxidation and synthesis, amino acid degradation, and the production of cholesterol and steroid hormones. The molecule functions by forming thioester bonds with acyl groups, enabling the transfer and activation of acetyl and other acyl moieties in biosynthetic and energy-generating pathways.
Without adequate coenzyme A biosynthesis, cells cannot maintain normal energy metabolism or synthesise critical lipid components of cellular membranes. The consequences of reduced CoA availability appear particularly severe in the brain, where high metabolic demands and complex lipid requirements make neural tissue especially vulnerable to disruptions in this pathway.
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Chromosome location
COASY is located at chromosome band 17q21.2 on the long arm of chromosome 17. This chromosomal region contains numerous genes involved in neurological function and metabolic processes. The COASY protein comprises 564 amino acids when fully translated.
Protein structure
The COASY protein contains two distinct functional domains that reflect its bifunctional enzymatic role. The phosphopantetheine adenylyltransferase domain spans amino acids 180 to 358 and is responsible for catalysing the addition of adenosine monophosphate to phosphopantetheine. The DPCK domain extends from amino acids 360 to 563 and performs the final phosphorylation step, converting dephospho-CoA into coenzyme A.
This modular architecture allows the protein to coordinate both enzymatic reactions efficiently, with the product of the first reaction immediately available as substrate for the second domain. The sequential arrangement of these catalytic regions within a single polypeptide chain represents an economical solution for executing consecutive steps in the same biosynthetic pathway.
Key variants
Pathogenic variants in COASY typically result in reduced enzymatic function, decreasing the cell's capacity to synthesise coenzyme A. Most reported disease-causing variants are inherited in an autosomal recessive manner, meaning an individual must inherit altered copies from both parents to develop the associated condition. Variants may affect either catalytic domain or regulatory regions that influence protein stability and expression levels.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1129C>T | p.Arg377Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Neurodegeneration with brain iron accumulation 6 |
c.1486-3C>G | - | Pathogenic/Likely pathogenic | ★★☆☆ | COASY-Related Disorders |
c.1495C>T | p.Arg499Cys | Pathogenic | ★★☆☆ | Neurodegeneration with brain iron accumulation 6 |
c.1549_1550del | p.Ser517fs | Pathogenic/Likely pathogenic | ★★☆☆ | Neurodegeneration with brain iron accumulation |
c.1567C>T | p.Gln523Ter | Pathogenic | ★★☆☆ | COASY-Related Disorders |
c.600dup | p.Asp201Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Neurodegeneration with brain iron accumulation 6 |
c.1068_1069del | p.Cys357fs | Pathogenic | ★☆☆☆ | Neurodegeneration with brain iron accumulation |
c.1401_1404dup | p.Ile469fs | Pathogenic | ★☆☆☆ | Neurodegeneration with brain iron accumulation 6 |
c.1579C>T | p.Gln527Ter | Pathogenic | ★☆☆☆ | Neurodegeneration with brain iron accumulation 6 |
c.183del | p.Phe62fs | Pathogenic | ★☆☆☆ | Neurodegeneration with brain iron accumulation 6 |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants inherited from both parents in COASY cause CoPAN (COASY protein-associated neurodegeneration), also known as a form of neurodegeneration with brain iron accumulation (NBIA). This rare autosomal recessive disorder typically presents in early childhood with dystonia, spasticity, developmental regression, and characteristic iron accumulation in the basal ganglia visible on magnetic resonance imaging. Affected individuals may experience progressive motor impairment, cognitive decline, and seizures. The condition falls within the broader category of neurodegeneration with brain iron accumulation disorders, a group of inherited conditions characterised by abnormal iron deposits in specific brain regions.
Inheritance pattern
Conditions caused by pathogenic COASY variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
COASY appears on multiple NHS Genomic Medicine Service gene panels reflecting its relevance to paediatric and adult neurological presentations. The gene holds green (high-evidence) gene-disease validity classification on panels including Childhood onset dystonia, chorea or related movement disorder, Early onset dystonia, Intellectual disability, Severe microcephaly, and Structural basal ganglia disorders. It is also listed on the Adult onset neurodegenerative disorder panel, Hereditary ataxia with onset in adulthood, and Fetal anomalies panels. This broad panel representation reflects the variable age of onset and clinical heterogeneity observed in COASY-related conditions, supporting genomic testing when clinical features align with impaired basal ganglia function or early-onset neurodegeneration.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the inheritance pattern of COASY-related conditions?
COASY-related neurodegeneration follows an autosomal recessive inheritance pattern. An individual must inherit a pathogenic variant from both parents to develop the condition. Carriers with one altered copy typically remain unaffected.
Why does COASY deficiency particularly affect the brain?
The brain has exceptionally high energy demands and relies heavily on coenzyme A-dependent metabolic pathways for energy production and lipid synthesis. Reduced coenzyme A availability appears to disproportionately impair neural tissue, particularly structures like the basal ganglia that coordinate movement and have high metabolic requirements.
Can COASY variants be detected through carrier screening?
Yes, COASY is included on neurogenetics carrier screening panels. Carrier screening can identify individuals who carry one pathogenic variant, which is particularly relevant for reproductive planning when both prospective parents are carriers of variants in the same gene.