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PYCR1

pyrroline-5-carboxylate reductase 1

The PYCR1 gene provides instructions for producing an enzyme crucial for proline synthesis and mitochondrial function, with variants linked to inherited connective tissue disorders such as cutis laxa type 2B. PYCR1 encodes pyrroline-5-carboxylate reductase 1, an enzyme located in the mitochondria.

Chromosome 17q25.3 Autosomal recessive HGNC:9721 Tier C
PYCR1 17q25.3 p arm q arm 17

PYCR1 is located on the long (q) arm of chromosome 17, at band 17q25.3. Arm ratio per GRCh38 - banding schematic.

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Clinical tests that include this

Carrier Screening panel
PYCR1 is 1 of 1,008 genes on this panel
Expanded carrier screening for recessive and X-linked conditions

Overview

The PYCR1 gene, full name pyrroline-5-carboxylate reductase 1, is essential for the production of the amino acid proline within the body. This gene's product, an enzyme, is located in the mitochondria, the cell's powerhouses, where it supports key metabolic processes. Understanding PYCR1 is important for comprehending certain inherited conditions that affect connective tissues.

What the gene does

The PYCR1 gene provides instructions for creating an enzyme that is critical for mitochondrial function and the synthesis of proline. Proline, an amino acid, is produced through a multi-step process from glutamate. The PYCR1 enzyme facilitates the final step of this pathway, converting pyrroline-5-carboxylate into proline. This conversion between proline and glutamate is vital for maintaining the supply of amino acids necessary for protein synthesis and for efficient energy transfer within cells. Therefore, PYCR1 plays a fundamental role in cellular metabolism and energy homeostasis.

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Chromosome location

The PYCR1 gene is situated on chromosome 17, specifically at position 17q25.3. This chromosomal location indicates where the gene can be found within the human genome, influencing its proximity to other genes and regulatory elements.

Protein structure

The PYCR1 protein, comprising 319 amino acids, includes a Disordered region spanning amino acids 294-319. This disordered region may contribute to the protein's flexibility and its ability to interact with other molecules within the cell.

Key variants

Genetic variations within the PYCR1 gene can alter the protein's structure or function. Such changes may lead to a disruption in proline metabolism or mitochondrial activity, impacting cellular processes. These variants can range from single nucleotide changes to larger deletions or insertions.

No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.

Associated conditions

Pathogenic variants in the PYCR1 gene are associated with inherited connective tissue disorders. One notable condition linked to PYCR1 variants is Cutis laxa type 2B. This condition is typically inherited in an autosomal recessive pattern and involves characteristic features related to skin elasticity and other systemic effects.

Inheritance pattern

Conditions caused by pathogenic PYCR1 variants typically follow autosomal recessive inheritance.

♀ Carrier parent 1 altered copy ♂ Carrier parent 1 altered copy Affected Carrier Carrier Unaffected Affected Carrier Unaffected Circles = females · Squares = males

When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.

Carrier frequency by population How common is heterozygous PYCR1 carrier status across ancestry groups?

UK clinical status

In the UK, the PYCR1 gene is recognised on several NHS Genomic Medicine Service national panels. It is listed as 'green' on the DDG2P panel, as well as on panels for Ehlers Danlos syndrome with a likely monogenic cause (R101), Foetal anomalies (R21), Intellectual disability, Likely inborn error of metabolism (R98), Skeletal dysplasia (R104), and Undiagnosed metabolic disorders, indicating its established clinical significance within these areas.

Green-listed
High evidence · clinically actionable in NHS testing
Included in NHS GMS signed-off panels
Ehlers Danlos syndrome with a likely monogenic cause · R101 NHS GMS → Fetal anomalies · R21 NHS GMS → Likely inborn error of metabolism · R98 NHS GMS → Skeletal dysplasia · R104 NHS GMS → DDG2P NHS GMS → Intellectual disability 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 is the role of the PYCR1 protein?

The PYCR1 protein is an enzyme found in mitochondria, where it plays a critical role in the final step of proline synthesis from pyrroline-5-carboxylate. This process is essential for maintaining cellular amino acid balance and energy transfer.

What health conditions are associated with variants in the PYCR1 gene?

Variants in the PYCR1 gene are primarily associated with autosomal recessive cutis laxa type 2B, an inherited condition characterised by loose, sagging skin and other distinctive features.

How is Cutis laxa type 2B inherited?

Cutis laxa type 2B linked to PYCR1 variants is inherited in an autosomal recessive manner. This means an individual must inherit two copies of the altered gene, one from each parent, to develop the condition.

References

  1. Dimopoulou A, Fischer B, Gardeitchik T. Genotype-phenotype spectrum of PYCR1-related autosomal recessive cutis laxa. Molecular genetics and metabolism. 2013. PMID: 24035636
  2. Guernsey DL, Jiang H, Evans SC. Mutation in pyrroline-5-carboxylate reductase 1 gene in families with cutis laxa type 2. American journal of human genetics. 2009. PMID: 19576563
  3. Reversade B, Escande-Beillard N, Dimopoulou A. Mutations in PYCR1 cause cutis laxa with progeroid features. Nature genetics. 2009. PMID: 19648921
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 27 September 2026. Content compiled from HGNC · MedlinePlus Genetics · ClinGen · Genomics England PanelApp · NHS National Genomic Test Directory · ClinVar · UniProt · AlphaFold .