ABO | |||||||||||||||||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||||||||||||||||||||||||||||
Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
Aliases | ABO , A3GALNT, A3GALT1, GTB, NAGAT, ABO blood group (transferase A, alpha 1-3-N-acetylgalactosaminyltransferase; transferase B, alpha 1-3-galactosyltransferase), alpha 1-3-N-acetylgalactosaminyltransferase and alpha 1-3-galactosyltransferase | ||||||||||||||||||||||||||||||||||||||||||||||||||
External IDs | OMIM: 110300 MGI: 2135738 HomoloGene: 69306 GeneCards: ABO | ||||||||||||||||||||||||||||||||||||||||||||||||||
EC number | 2.4.1.37 2.4.1.40, 2.4.1.37 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
|
Histo-blood group ABO system transferase is an enzyme with glycosyltransferase activity, which is encoded by the ABO gene in humans. [5] [6] It is ubiquitously expressed in many tissues and cell types. [7] ABO determines the ABO blood group of an individual by modifying the oligosaccharides on cell surface glycoproteins. Variations in the sequence of the protein between individuals determine the type of modification and the blood group. The ABO gene also contains one of 27 SNPs associated with increased risk of coronary artery disease. [8]
The ABO gene resides on chromosome 9 at the band 9q34.2 and contains 7 exons. [6] The ABO locus encodes three alleles, that is, 3 variants of the same gene. One allele is derived from each parent.
The A allele produces α-1,3-N-acetylgalactosamine transferase (A-transferase), which catalyzes the transfer of GalNAc residues from the UDP-GalNAc donor nucleotide to the Gal residues of the acceptor H antigen, converting the H antigen into A antigen in A and AB individuals.
The B allele encodes α-1,3-galactosyl transferase (B-transferase), which catalyzes the transfer of Gal residues from the UDP-Gal donor nucleotide to the Gal residues of the acceptor H antigen, converting the H antigen into B antigen in B and AB individuals. Remarkably, the difference between the A and B glycosyltransferase enzymes is only four amino acids. [9]
The O allele lacks both enzymatic activities because of the frameshift caused by a deletion of guanine-258 in the gene which corresponds to a region near the N-terminus of the protein. [10] This results in a frameshift and thus of a truncated protein of only 117 amino acids. [9] [11] The truncated protein is unable to modify oligosaccharides which end in fucose linked to galactose. Thus no A or B antigen is found in O individuals. This sugar combination is termed the H antigen. These antigens play an important role in the match of blood transfusion and organ transplantation. [9] Other minor alleles have been found for this gene. [6]
There are six common alleles in individuals of European descent. Nearly every living human's phenotype for the ABO gene is some combination of just these six alleles: [12] [13]
Many rare variants of these alleles have been found in human populations around the world.
In human cells, the ABO alleles and their encoded glycosyltransferases have been described in several oncologic conditions. [14] Using anti-GTA/GTB monoclonal antibodies, it was demonstrated that a loss of these enzymes was correlated to malignant bladder and oral epithelia. [15] [16] Furthermore, the expression of ABO blood group antigens in normal human tissues is dependent upon the type of differentiation of the epithelium. In most human carcinomas, including oral carcinoma, a significant event as part of the underlying mechanism is decreased expression of the A and B antigens. [17] Several studies have observed that a relative down-regulation of GTA and GTB occurs in oral carcinomas in association with tumor development. [17] [18] More recently, a genome wide association study (GWAS) has identified variants in the ABO locus associated with susceptibility to pancreatic cancer. [19] [20]
A multi-locus genetic risk score study based on a combination of 27 loci, including the ABO gene, identified individuals at increased risk for both incident and recurrent coronary artery disease events, as well as an enhanced clinical benefit from statin therapy. The study was based on a community cohort study (the Malmo Diet and Cancer study) and four additional randomized controlled trials of primary prevention cohorts (JUPITER and ASCOT) and secondary prevention cohorts (CARE and PROVE IT-TIMI 22). [8]
An allele, or allelomorph, is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule.
In biochemistry, a transferase is any one of a class of enzymes that catalyse the transfer of specific functional groups from one molecule to another. They are involved in hundreds of different biochemical pathways throughout biology, and are integral to some of life's most important processes.
The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. For human blood transfusions, it is the most important of the 44 different blood type classification systems currently recognized by the International Society of Blood Transfusions (ISBT) as of December 2022. A mismatch in this, or any other serotype, can cause a potentially fatal adverse reaction after a transfusion, or an unwanted immune response to an organ transplant. The associated anti-A and anti-B antibodies are usually IgM antibodies, produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses.
α-Galactosidase is a glycoside hydrolase enzyme that catalyses the following reaction:
Glycosyltransferases are enzymes that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur-based.
The Kell antigen system is a human blood group system, that is, a group of antigens on the human red blood cell surface which are important determinants of blood type and are targets for autoimmune or alloimmune diseases which destroy red blood cells. The Kell antigens are K, k, Kpa, Kpb, Jsa and Jsb. The Kell antigens are peptides found within the Kell protein, a 93-kilodalton transmembrane zinc-dependent endopeptidase which is responsible for cleaving endothelin-3.
Beta-hexosaminidase subunit beta is an enzyme that in humans is encoded by the HEXB gene.
The Lewis antigen system is a human blood group system. It is based upon two genes on chromosome 19: FUT3, or Lewis gene; and FUT2, or Secretor gene. Both genes are expressed in glandular epithelia. FUT2 has a dominant allele which codes for an enzyme and a recessive allele which does not produce a functional enzyme. Similarly, FUT3 has a functional dominant allele (Le) and a non-functional recessive allele (le).
Hexosaminidase A (alpha polypeptide), also known as HEXA, is an enzyme that in humans is encoded by the HEXA gene, located on the 15th chromosome.
In enzymology, a glycoprotein-fucosylgalactoside alpha-N-acetylgalactosaminyltransferase is an enzyme that catalyzes the chemical reaction
Galactoside 3(4)-L-fucosyltransferase is an enzyme that in humans is encoded by the FUT3 gene.
Glycophorin B (MNS blood group) (gene designation GYPB) also known as sialoglycoprotein delta and SS-active sialoglycoprotein is a protein which in humans is encoded by the GYPB gene. GYPB has also recently been designated CD235b (cluster of differentiation 235b).
Galactoside 2-alpha-L-fucosyltransferase 2 is an enzyme that in humans is encoded by the FUT2 gene. It affects the secretor status of ABO antigens.
Polypeptide N-acetylgalactosaminyltransferase 3 is an enzyme that in humans is encoded by the GALNT3 gene.
Mucin-7 is a protein that in humans is encoded by the MUC7 gene. In animals, the MUC7 gene is found in most placental mammals, but not marsupials.
N-acetyllactosaminide beta-1,6-N-acetylglucosaminyl-transferase is an enzyme that in humans is encoded by the GCNT2 gene.
Beta-1,4 N-acetylgalactosaminyltransferase 1 is an enzyme that in humans is encoded by the B4GALNT1 gene.
Polypeptide N-acetylgalactosaminyltransferase 6 is an enzyme that in humans is encoded by the GALNT6 gene.
Beta-1,4 N-acetylgalactosaminyltransferase 2 is an enzyme that in humans is encoded by the B4GALNT2 gene.
Cis AB is a type of rare mutation in the ABO gene. It happens when the transferase allele contains a mix of amino acids from either A or B alleles, producing a bifunctional enzyme that can produce both types of antigens, usually with one weaker than the other. This results in a serum test result much like the standard, separate (trans) AB phenotype, although the weaker antigen can occasionally fail to be detected. It complicates the basic inheritance pattern and blood-transfusion compatibility matching for ABO blood typing.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.