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ACP5

acid phosphatase 5, tartrate resistant

The ACP5 gene provides instructions for producing the tartrate-resistant acid phosphatase (TRAP) enzyme, which plays a key role in bone remodelling and immune system regulation. The ACP5 gene is responsible for encoding the TRAP enzyme, essential for various biological processes.

Chromosome 19p13.2 HGNC:124 Tier C
ACP5 19p13.2 p arm q arm 19

ACP5 is located on the short (p) arm of chromosome 19, at band 19p13.2. Arm ratio per GRCh38 - banding schematic.

Explore chromosome 19 in the library →

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Clinical tests that include this

Carrier Screening panel
ACP5 is 1 of 1,008 genes on this panel
Expanded carrier screening for recessive and X-linked conditions

Overview

The ACP5 gene, also known as acid phosphatase 5, tartrate resistant, is vital for proper bone and immune system function. It provides the genetic blueprint for an enzyme called tartrate-resistant acid phosphatase (TRAP), which exists in two main forms: TRAP5a and TRAP5b.

TRAP5a is predominantly found in immune cells, while TRAP5b is primarily located in osteoclasts, which are specialised bone cells. Disruptions in the ACP5 gene can lead to conditions affecting both skeletal development and immune regulation.

What the gene does

The TRAP enzyme, encoded by the ACP5 gene, regulates the activity of osteopontin, a protein active in bone and immune cells. In osteoclasts, TRAP5b is crucial for bone remodelling. Initially, osteopontin allows osteoclasts to attach to bone tissue for resorption. Once bone breakdown is complete, TRAP5b inactivates osteopontin, causing the osteoclasts to detach, thus completing the remodelling cycle.

In the immune system, TRAP5a functions in macrophages and dendritic cells. Here, osteopontin promotes inflammation and helps regulate immune cell activity to combat pathogens. Similar to its role in bone cells, TRAP5a inactivates osteopontin in immune cells when its activity is no longer required, helping to modulate immune responses effectively.

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Chromosome location

The ACP5 gene is situated on the short arm of chromosome 19, specifically at band 19p13.2. This genomic location indicates its position within the human genome.

Protein structure

The protein encoded by the ACP5 gene is 325 amino acids long. It contains a specific functional region known as the Inhibitory loop, which spans amino acids 162-179. This domain is critical for the enzyme's regulatory function.

Domain map · 325 amino acids
Inhibitory loop (162-179)Inhibitory loop162-1791~163325
Region - functional region
🧬 Explore 3D structure on AlphaFold
UniProt:P13686Length:325 aaStructure:AlphaFold

Key variants

Variants in the ACP5 gene can alter the function of the TRAP enzyme. These genetic changes can range from single amino acid substitutions to alterations that result in a shortened, non-functional protein. Such variants may disrupt the enzyme's role in bone remodelling or immune system regulation.

340
Total variants catalogued in ClinVar
View all on ClinVar →
38 Pathogenic / Likely pathogenic 156 Uncertain significance 138 Benign / Likely benign 8 Conflicting or other

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.222C>A
single nucleotide variant
 p.Tyr74Ter Pathogenic/Likely pathogenic ★★☆☆ ACP5-related disorder
c.325G>A
single nucleotide variant
 p.Gly109Arg Pathogenic/Likely pathogenic ★★☆☆ ACP5-related disorder
c.369C>A
single nucleotide variant
 p.Tyr123Ter Pathogenic ★★☆☆ ACP5-related disorder
c.526C>T
single nucleotide variant
 p.Arg176Ter Pathogenic ★★☆☆ Inborn genetic diseases
c.550C>T
single nucleotide variant
 p.Gln184Ter Pathogenic/Likely pathogenic ★★☆☆ ACP5-related disorder
c.643G>A
single nucleotide variant
 p.Gly215Arg Pathogenic/Likely pathogenic ★★☆☆ ACP5-related disorder
c.738C>A
single nucleotide variant
 p.Tyr246Ter Pathogenic/Likely pathogenic ★★☆☆ Spondyloenchondrodysplasia with immune dysregulation
c.772_790del
Deletion
 p.Ser258fs Pathogenic/Likely pathogenic ★★☆☆ Spondyloenchondrodysplasia with immune dysregulation
c.791T>A
single nucleotide variant
 p.Met264Lys Pathogenic/Likely pathogenic ★★☆☆ Spondyloenchondrodysplasia with immune dysregulation
c.799del
Deletion
 p.Ser267fs Pathogenic ★★☆☆ Spondyloenchondrodysplasia with immune dysregulation

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

Variants in the ACP5 gene are associated with spondyloenchondrodysplasia with immune dysregulation (SPENCDI). This condition is characterised by specific abnormalities in bone growth and significant immune system dysfunction. Research has identified at least 10 different mutations in the ACP5 gene that contribute to SPENCDI, typically involving changes to single protein building blocks or leading to the production of an abnormally short enzyme.

No disease links recorded for this gene in our reference set.

UK clinical status

The ACP5 gene is recognised within the NHS Genomic Medicine Service due to its clinical relevance. It is part of several Green status panels in PanelApp, indicating that there is strong evidence for its association with specific conditions. These include COVID-19 research, Developmental Disorders Gene (DDG2P), Foetal anomalies (R21), Intracerebral calcification disorders, Primary immunodeficiency or monogenic inflammatory bowel disease (R15), Skeletal dysplasia (R104), and White matter disorders and cerebral calcification - childhood onset.

Green-listed
High evidence · clinically actionable in NHS testing
Included in NHS GMS signed-off panels
Fetal anomalies · R21 NHS GMS → Primary immunodeficiency or monogenic inflammatory bowel disease · R15 NHS GMS → Skeletal dysplasia · R104 NHS GMS → DDG2P NHS GMS → White matter disorders and cerebral calcification - childhood onset NHS GMS →
NHS Genomic Medicine Service Jeen carrier screening

Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory

Frequently asked questions

What does the ACP5 gene do?

The ACP5 gene provides instructions for making the tartrate-resistant acid phosphatase (TRAP) enzyme. This enzyme plays a crucial role in regulating osteopontin activity, which is important for bone breakdown and remodelling, as well as for modulating immune responses.

What conditions are associated with the ACP5 gene?

Variants in the ACP5 gene are associated with spondyloenchondrodysplasia with immune dysregulation (SPENCDI). This condition affects both bone growth and immune system function.

Where is the ACP5 gene located?

The ACP5 gene is located on chromosome 19, specifically at position 19p13.2.

References

  1. Lausch E, Janecke A, Bros M. Genetic deficiency of tartrate-resistant acid phosphatase associated with skeletal dysplasia, cerebral calcifications and autoimmunity. Nature genetics. 2011. PMID: 21217752
  2. Briggs TA, Rice GI, Daly S. Tartrate-resistant acid phosphatase deficiency causes a bone dysplasia with autoimmunity and a type I interferon expression signature. Nature genetics. 2011. PMID: 21217755
  3. Behrens TW, Graham RR. TRAPing a new gene for autoimmunity. Nature genetics. 2011. PMID: 21270835
  4. Hayman AR. Tartrate-resistant acid phosphatase (TRAP) and the osteoclast/immune cell dichotomy. Autoimmunity. 2008. PMID: 18365835
Educational content. This page is not medical or genetic advice, is not individually reviewed by a clinician for each reader, and should not replace a consultation with a qualified healthcare professional or genetic counsellor. If you are considering genetic testing or acting on a test result, book a consultation.
Data sources Last updated 18 October 2026. Content compiled from HGNC · MedlinePlus Genetics · ClinGen · Genomics England PanelApp · NHS National Genomic Test Directory · ClinVar · UniProt · AlphaFold .