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PPT1
palmitoyl-protein thioesterase 1
The PPT1 gene provides instructions for producing an enzyme called palmitoyl-protein thioesterase 1, which plays a crucial role in breaking down fats attached to proteins within cellular lysosomes. The PPT1 gene is responsible for making an enzyme that helps to remove specific fatty acids from proteins, a process vital for cellular waste management.
PPT1 is located on the short (p) arm of chromosome 1, at band 1p34.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The PPT1 gene encodes palmitoyl-protein thioesterase 1, an enzyme critical for the proper functioning of lysosomes, which are cellular compartments responsible for waste breakdown and recycling. This enzyme specifically removes certain long-chain fatty acids from proteins, primarily palmitate.
This enzymatic action is essential for cells to effectively degrade and recycle proteins no longer required. Beyond its role in protein degradation, the PPT1 enzyme is also thought to contribute to the development of synapses, which are specialised junctions that enable neuronal signalling.
What the gene does
The palmitoyl-protein thioesterase 1 enzyme, encoded by the PPT1 gene, functions primarily within cellular lysosomes. Its main role involves a specific type of chemical reaction where it removes fatty acids, particularly palmitate, from proteins. This enzymatic activity is crucial for the efficient breakdown and recycling of proteins within the cell.
Cleavage of these fatty acid modifications facilitates the degradation pathway of proteins, preventing their accumulation. This function is vital for maintaining cellular health and preventing the buildup of unwanted materials. Research also indicates a potential involvement of PPT1 in neurodevelopment, specifically in the formation of synapses, which are key for neuronal communication.
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Chromosome location
The PPT1 gene is located on chromosome 1, specifically at position 1p34.2. This genomic location refers to the short (p) arm of chromosome 1, within region 34.2. The gene provides the genetic blueprint for a protein consisting of 306 amino acids.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Variants within the PPT1 gene can alter the function or production of the palmitoyl-protein thioesterase 1 enzyme. Over 65 different pathogenic variants have been identified in this gene. These genetic changes can impair the enzyme's ability to effectively remove fatty acids from proteins, leading to a buildup of cellular waste products.
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.18C>A | p.Cys6Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.1A>C | p.Met1Leu | Pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.289_290del | p.Gln97fs | Pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.29_41del | p.Leu10fs | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.30_42dup | p.Leu15fs | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.442G>T | p.Gly148Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.541G>C | p.Val181Leu | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.628-2A>G | - | Pathogenic/Likely pathogenic | ★★☆☆ | PPT1-related disorder |
c.629_630dup | p.Ile211fs | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
c.637G>T | p.Glu213Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Neuronal ceroid lipofuscinosis 1 |
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 in the PPT1 gene are primarily associated with Batten disease (CLN1), also known as infantile neuronal ceroid lipofuscinosis. This inherited disorder typically manifests with progressive neurological deterioration affecting cognitive abilities, speech acquisition, and ambulatory skills. Individuals often experience repeated epileptic episodes and progressive vision loss, with symptoms usually appearing by 18 months of age, though later onset can occur.
Inheritance pattern
Conditions caused by pathogenic PPT1 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
The PPT1 gene is included in several expert-reviewed NHS Genomic Medicine Service (GMS) national panels. These include panels for DDG2P, Early onset or syndromic epilepsy, Intellectual disability, Likely inborn error of metabolism, Lysosomal storage disorder, Neuronal ceroid lipofuscinosis, Retinal disorders, and Undiagnosed metabolic disorders, indicating its clinical relevance in the UK healthcare system.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the PPT1 gene?
The PPT1 gene provides instructions for an enzyme called palmitoyl-protein thioesterase 1. This enzyme catalyses lipid removal from modified proteins in lysosomal compartments, enabling cellular waste processing and molecular turnover.
Which condition is most commonly associated with PPT1 gene variants?
Variants in the PPT1 gene are primarily associated with Batten disease (CLN1), a progressive neurodegenerative disorder characterised by cognitive decline, motor regression, epilepsy, and visual impairment.
How does the PPT1 enzyme contribute to cellular health?
By removing fatty acid modifications from proteins, the PPT1 enzyme facilitates the proper degradation and recycling of proteins, which is crucial for preventing the accumulation of waste products and maintaining overall cell function.
References
- Kollmann K, Uusi-Rauva K, Scifo E. Cell biology and function of neuronal ceroid lipofuscinosis-related proteins. Biochimica et biophysica acta. 2013. PMID: 23402926
- Hawkins-Salsbury JA, Cooper JD, Sands MS. Pathogenesis and therapies for infantile neuronal ceroid lipofuscinosis (infantile CLN1 disease). Biochimica et biophysica acta. 2013. PMID: 23747979
- Kousi M, Lehesjoki AE, Mole SE. Update of the mutation spectrum and clinical correlations of over 360 mutations in eight genes that underlie the neuronal ceroid lipofuscinoses. Human mutation. 2012. PMID: 21990111
- Jalanko A, Braulke T. Neuronal ceroid lipofuscinoses. Biochimica et biophysica acta. 2009. PMID: 19084560
- Simonati A, Tessa A, Bernardina BD. Variant late infantile neuronal ceroid lipofuscinosis because of CLN1 mutations. Pediatric neurology. 2009. PMID: 19302939
- Kim SJ, Zhang Z, Sarkar C. Palmitoyl protein thioesterase-1 deficiency impairs synaptic vesicle recycling at nerve terminals, contributing to neuropathology in humans and mice. The Journal of clinical investigation. 2008. PMID: 18704195
- Ramadan H, Al-Din AS, Ismail A. Adult neuronal ceroid lipofuscinosis caused by deficiency in palmitoyl protein thioesterase 1. Neurology. 2007. PMID: 17261688
- Das AK, Lu JY, Hofmann SL. Biochemical analysis of mutations in palmitoyl-protein thioesterase causing infantile and late-onset forms of neuronal ceroid lipofuscinosis. Human molecular genetics. 2001. PMID: 11440996