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Gene

AHCY

adenosylhomocysteinase

Summary

Cytogenetic location
20q11.22
Coordinates
Chromosome 20: 34,280,268–34,303,355 (GRCh38)
Exons
10 exons across 23.1 kb
Protein
432 amino acids
Inheritance
Autosomal recessive
Also known as
SAHH, AdoHcyase
MANE Select transcript
ENST00000217426.7NM_000687.4
Locus type
gene with protein product
  • Very high
  • Confident
  • Low
  • Very low

Reference genomeGRCh38

Positions on gene and variant pages follow this choice, in this browser.

Curated report relevant to this gene

  • Homocystinuria & Cobalamin Disorders

    • S-Adenosylhomocysteine Hydrolase DeficiencyAutosomal recessive

      Caused by variants in AHCY, which can cause muscle weakness, developmental delay and liver problems.

      • ClinGen rates the link definitive
      • 3 GenCC submitters rate it definitive or strong
      What knowing changes

      Knowing allows a methionine-restricted diet and supplements, which can improve some features.

Inheritance

Autosomal recessive
It takes a changed copy from each parent. With one, you are a carrier and usually unaffected; when both parents are carriers, each child has a one-in-four chance of inheriting two.

How AHCY is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
  • Stretches short reads find hard
Chromosome 20, with a bracket where AHCY sits. AHCY and 12 genes near it on chromosome 20, from 33,791,812 to 34,791,811.Chromosome 2020q11.22p13p12.3p12.2p12.1p11.23p11.22p11.21p11.1q11.1q11.21q11.22q11.23q12q13.11q13.12q13.13q13.2q13.31q13.32q13.3333.8 Mb34 Mb34.2 Mb34.4 Mb34.6 MbZNF341: 33,731,657–33,792,269, forward strandZNF341CHMP4B: 33,811,253–33,854,366, forward strandCHMP4BRALY: 33,993,632–34,108,308, forward strandRALYEIF2S2: 34,088,309–34,112,284, reverse strandEIF2S2ASIP: 34,194,569–34,269,346, forward strandASIPAHCY: 34,280,268–34,303,355, reverse strandAHCYITCH: 34,363,235–34,511,773, forward strandITCH: 34,363,271–34,540,923, forward strandDYNLRB1: 34,515,600–34,540,958, forward strandDYNLRB1MAP1LC3A: 34,546,838–34,560,357, forward strandMAP1LC3APIGU: 34,560,542–34,698,790, reverse strandPIGUNCOA6: 34,689,097–34,825,739, reverse strandNCOA6TP53INP2: 34,701,662–34,713,442, forward strandTP53INP2Diagram of AHCY: 10 exons on the reverse strand of chromosome 20Exon 9: 1 known disease-causing siteExon 8: 1 known disease-causing siteExon 6: 1 known disease-causing siteExon 4: 3 known disease-causing sitesExon 3: 3 known disease-causing sitesExon 2: 4 known disease-causing sitesExon 1: 1 known disease-causing siteExon 10: 34,280,268–34,281,165, 898 basesExon 9: 34,285,440–34,285,634, 195 basesExon 8: 34,290,332–34,290,449, 118 basesExon 7: 34,290,551–34,290,638, 88 basesExon 6: 34,290,731–34,290,938, 208 basesExon 5: 34,291,419–34,291,531, 113 basesExon 4: 34,292,358–34,292,507, 150 basesExon 3: 34,294,081–34,294,156, 76 basesExon 2: 34,295,395–34,295,585, 191 basesExon 1: 34,303,243–34,303,355, 113 bases10864215′3′

Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.

Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).

Nearby genes from Ensembl release 116, on GRCh38.

Exons make up 2.2 kb of the gene's 23.1 kb; 1,299 of those bases code for the protein.

How a genome test reads AHCY

17

positions in AHCY where ClinVar classes a change as pathogenic or likely pathogenic

None of them falls in a region short reads find hard.

A whole genome covers all 23.1 kb of AHCY, introns included, not only the 2.2 kb of exons.

Where this comes from

  • HGNC: the gene's symbol, name, other symbols and location.
  • MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
  • GenCC and ClinGen, released 2026-10-16: which conditions the gene is linked to, and how strongly.
  • The ACMG secondary findings list, SF v3.2.
  • ClinVar and the GIAB stratifications: known disease-causing sites, and the regions short reads find hard.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
  • Data release 2026.10.16-c6eea6bf.

Cite this page

APA

Dante Labs. (n.d.). AHCY gene: adenosylhomocysteinase. Retrieved 17 October 2026, from https://dantelabs.com/genes/ahcy

Vancouver

Dante Labs. AHCY gene: adenosylhomocysteinase [Internet]. [cited 17 October 2026]. Available from: https://dantelabs.com/genes/ahcy

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