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Gene

SI

sucrase-isomaltase

Summary

Cytogenetic location
3q26.1
Coordinates
Chromosome 3: 164,978,898–165,078,496 (GRCh38)
Exons
48 exons across 99.6 kb
Protein
1,827 amino acids
Inheritance
Autosomal recessive
MANE Select transcript
ENST00000264382.8NM_001041.4
Locus type
gene with protein product

Reference genomeGRCh38

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

Curated report relevant to this gene

  • Congenital Disaccharidase Deficiencies

    • Congenital sucrase-isomaltase deficiency (CSID)Autosomal recessive

      A deficiency of the sucrase-isomaltase enzyme, caused by SI variants, that impairs digestion of sucrose and some starches.

      • 3 GenCC submitters rate it definitive or strong
      What knowing changes

      Dietary restriction of sucrose and starch, with sacrosidase enzyme replacement, controls symptoms, and a diagnosis can explain long-standing IBS-like symptoms.

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 SI is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
  • Stretches short reads find hard
Chromosome 3, with a bracket where SI sits. SI and 1 gene near it on chromosome 3, from 164,528,697 to 165,528,696.Chromosome 33q26.1p26.3p26.2p26.1p25.3p25.2p25.1p24.3p24.2p24.1p23p22.3p22.2p22.1p21.33p21.32p21.31p21.2p21.1p14.3p14.2p14.1p13p12.3p12.2p12.1p11.2p11.1q11.1q11.2q12.1q12.2q12.3q13.11q13.12q13.13q13.2q13.31q13.32q13.33q21.1q21.2q21.3q22.1q22.2q22.3q23q24q25.1q25.2q25.31q25.32q25.33q26.1q26.2q26.31q26.32q26.33q27.1q27.2q27.3q28q29164.6 Mb164.8 Mb165 Mb165.2 Mb165.4 MbSI: 164,978,898–165,078,496, reverse strandSISLITRK3: 165,186,325–165,197,109, reverse strandSLITRK3Diagram of SI: 48 exons on the reverse strand of chromosome 3Exon 46: 1 known disease-causing siteExon 41: 1 known disease-causing siteExon 40: 1 known disease-causing siteExon 39: 1 known disease-causing siteExon 37: 2 known disease-causing sitesExon 36: 3 known disease-causing sitesExon 35: 3 known disease-causing sitesExon 33: 1 known disease-causing siteExon 31: 1 known disease-causing siteExon 30: 4 known disease-causing sitesExon 29: 1 known disease-causing siteExon 28: 2 known disease-causing sitesExon 27: 4 known disease-causing sitesExon 26: 1 known disease-causing siteExon 25: 2 known disease-causing sitesExon 24: 2 known disease-causing sitesExon 22: 1 known disease-causing siteExon 21: 1 known disease-causing siteExon 19: 1 known disease-causing siteExon 18: 3 known disease-causing sitesExon 17: 1 known disease-causing siteExon 16: 3 known disease-causing sitesExon 15: 2 known disease-causing sitesExon 14: 1 known disease-causing siteExon 13: 1 known disease-causing siteExon 12: 1 known disease-causing siteExon 10: 1 known disease-causing siteExon 8: 4 known disease-causing sitesExon 7: 2 known disease-causing sitesExon 6: 2 known disease-causing sitesExon 5: 2 known disease-causing sitesExon 4: 2 known disease-causing sitesExon 48: 164,978,898–164,979,430, 533 basesExon 47: 164,982,243–164,982,410, 168 basesExon 46: 164,983,002–164,983,051, 50 basesExon 45: 164,987,138–164,987,226, 89 basesExon 44: 164,991,353–164,991,477, 125 basesExon 43: 164,992,177–164,992,233, 57 basesExon 42: 164,992,313–164,992,397, 85 basesExon 41: 164,994,257–164,994,405, 149 basesExon 40: 164,996,535–164,996,651, 117 basesExon 39: 164,996,738–164,996,772, 35 basesExon 38: 164,998,540–164,998,673, 134 basesExon 37: 165,006,816–165,006,954, 139 basesExon 36: 165,007,911–165,007,998, 88 basesExon 35: 165,009,279–165,009,395, 117 basesExon 34: 165,012,980–165,013,042, 63 basesExon 33: 165,015,123–165,015,233, 111 basesExon 32: 165,015,952–165,016,080, 129 basesExon 31: 165,017,548–165,017,673, 126 basesExon 30: 165,017,761–165,017,873, 113 basesExon 29: 165,017,970–165,018,066, 97 basesExon 28: 165,019,602–165,019,770, 169 basesExon 27: 165,021,229–165,021,383, 155 basesExon 26: 165,023,570–165,023,776, 207 basesExon 25: 165,030,712–165,030,867, 156 basesExon 24: 165,032,522–165,032,692, 171 basesExon 23: 165,033,395–165,033,444, 50 basesExon 22: 165,036,389–165,036,477, 89 basesExon 21: 165,037,900–165,038,024, 125 basesExon 20: 165,039,078–165,039,134, 57 basesExon 19: 165,039,887–165,039,971, 85 basesExon 18: 165,040,940–165,041,094, 155 basesExon 17: 165,043,059–165,043,175, 117 basesExon 16: 165,046,841–165,047,012, 172 basesExon 15: 165,049,127–165,049,244, 118 basesExon 14: 165,049,791–165,049,875, 85 basesExon 13: 165,055,194–165,055,307, 114 basesExon 12: 165,058,963–165,059,082, 120 basesExon 11: 165,059,168–165,059,299, 132 basesExon 10: 165,059,902–165,060,027, 126 basesExon 9: 165,062,371–165,062,483, 113 basesExon 8: 165,063,442–165,063,541, 100 basesExon 7: 165,065,261–165,065,432, 172 basesExon 6: 165,067,340–165,067,491, 152 basesExon 5: 165,068,722–165,068,831, 110 basesExon 4: 165,069,078–165,069,195, 118 basesExon 3: 165,074,531–165,074,667, 137 basesExon 2: 165,075,895–165,076,012, 118 basesExon 1: 165,078,433–165,078,496, 64 bases484540353025201510515′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 6 kb of the gene's 99.6 kb; 5,484 of those bases code for the protein.

How a genome test reads SI

73

positions in SI 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 99.6 kb of SI, introns included, not only the 6 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.). SI gene: sucrase-isomaltase. Retrieved 16 October 2026, from https://dantelabs.com/genes/si

Vancouver

Dante Labs. SI gene: sucrase-isomaltase [Internet]. [cited 16 October 2026]. Available from: https://dantelabs.com/genes/si

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