HGNC Approved Gene Symbol: AMY2B
Cytogenetic location: 1p21.1 Genomic coordinates (GRCh38): 1:103,554,644-103,579,534 (from NCBI)
Alpha-amylases catalyze the hydrolysis of alpha-1,4 glucan linkages in starch. Initially, salivary alpha-amylase (see AMY1A, 104700) provides a partial digestion, which breaks down polymeric starch into shorter oligomers. Upon reaching the gut, this partially digested starch is extensively hydrolyzed into smaller oligosaccharides by the alpha-amylase synthesized in the pancreas (AMY2B; AMY2A, 104650) and excreted into the lumen (summary by Brayer et al., 1995).
Brayer et al. (1995) stated that human alpha-amylase is composed of 496 amino acids.
Using a human genomic DNA segment that hybridizes with rat pancreatic amylase cDNA to study human-mouse somatic cell hybrids, Tricoli and Shows (1984) assigned the amylase gene(s) to region 1p22-p21. The human cell studied in the hybrid had a translocation involving chromosome 1. RFLPs at the amylase loci were described.
Groot et al. (1988) suggested that there are 2 pancreatic amylase genes in the human genome, designated AMY2A and AMY2B. Pronk et al. (1982) presented evidence they interpreted as indicating duplication of the salivary amylase locus also.
In a full exposition of the structure of the part of the genome containing the alpha-amylase multigene family, Groot et al. (1989) described 2 haplotypes consisting of different numbers of salivary amylase genes: the short haplotype contains 2 pancreatic genes, termed by them AMY2A and AMY2B, and 1 salivary amylase gene, termed by them AMY1C, arranged in the order 2B-2A-1C and encompassing a total length of approximately 100 kb. The long haplotype spans about 300 kb and contains 6 additional genes arranged in 2 repeats, each of which consists of 2 salivary amylase genes, designated AMY1A (104700) and AMY1B (104701), and a pseudogene lacking the first 3 exons (AMYP1). The order of the amylase genes within the repeat is 1A-1B-P1. All genes are in a head-to-tail orientation except AMY1B, which has a reverse orientation with respect to the other genes. A general designation 2B-2A-(1A-1B-P)n-1C can describe these haplotypes, n being 0 and 2 for the short and long haplotypes, respectively. Groot et al. (1989) presented evidence for the existence of additional haplotypes.
Groot et al. (1990) proposed that the alpha-amylase multigene family evolved through unequal, homologous, inter- and intrachromosomal crossovers. Groot et al. (1991) reported observations on polymorphic DNA patterns and interpreted them in light of this hypothesis.
Polymorphism of AMY2B was determined by agar gel electrophoresis. Data on gene frequencies of allelic variants were tabulated by Roychoudhury and Nei (1988).
Using a combination of high-precision measurement methods with segregation analysis, Carpenter et al. (2015) determined that most amylase haplotypes worldwide contain odd numbers of AMY1 repeat units, but that haplotypes carrying even numbers of AMY1 repeats are associated with rearrangements giving rise to CNV of the pancreatic amylase genes AMY2A/2B. As a consequence, the copy numbers of AMY1 and AMY2A/2B are numerically correlated. Data from different paralog ratio tests (PRTs) led to the experimental and read-depth characterization of 4 distinct CNV classes affecting AMY2 genes: a deletion of about 75 kb affecting AMY2A (and AMY1); a duplication of about 116 kb including both AMY2A and AMY2B (and a copy of AMY1); higher-order expansions of AMY2A and AMY2B; and an independent duplication of AMY2A but not AMY2B. Among the regional population groupings used by the 1000 Genomes Project, East Asian populations display few AMY2 variations and nearly all individuals have an even AMY1 diploid copy number; deletions of AMY2 are common among the European and American samples, and duplications of AMY2A/2B are at highest frequency in African samples.
Brayer, G. D., Luo, Y., Withers, S. G. The structure of human pancreatic alpha-amylase at 1.8 angstrom resolution and comparisons with related enzymes. Protein Sci. 4: 1730-1742, 1995. [PubMed: 8528071] [Full Text: https://doi.org/10.1002/pro.5560040908]
Carpenter, D., Dhar, S., Mitchell, L. M., Fu, B., Tyson, J., Shwan, N. A. A., Ynag, F., Thomas, M. G., Armour, J. A. L. Obesity, starch digestion and amylase: association between copy number variants at human salivary (AMY1) and pancreatic (AMY2) amylase genes. Hum. Molec. Genet. 24: 3472-3480, 2015. [PubMed: 25788522] [Full Text: https://doi.org/10.1093/hmg/ddv098]
Groot, P. C., Bleeker, M. J., Pronk, J. C., Arwert, F., Mager, W. H., Planta, R. J., Eriksson, A. W., Frants, R. R. Human pancreatic amylase is encoded by two different genes. Nucleic Acids Res. 16: 4724 only, 1988. [PubMed: 3260028] [Full Text: https://doi.org/10.1093/nar/16.10.4724]
Groot, P. C., Bleeker, M. J., Pronk, J. C., Arwert, F., Mager, W. H., Planta, R. J., Eriksson, A. W., Frants, R. R. The human alpha-amylase multigene family consists of haplotypes with variable numbers of genes. Genomics 5: 29-42, 1989. [PubMed: 2788608] [Full Text: https://doi.org/10.1016/0888-7543(89)90083-9]
Groot, P. C., Mager, W. H., Frants, R. R. Interpretation of polymorphic DNA patterns in the human alpha-amylase multigene family. Genomics 10: 779-785, 1991. [PubMed: 1679752] [Full Text: https://doi.org/10.1016/0888-7543(91)90463-o]
Groot, P. C., Mager, W. H., Henriquez, N. V., Pronk, J. C., Arwert, F., Planta, R. J., Eriksson, A. W., Frants, R. R. Evolution of the human alpha-amylase multigene family through unequal, homologous, and inter- and intrachromosomal crossovers. Genomics 8: 97-105, 1990. [PubMed: 2081604] [Full Text: https://doi.org/10.1016/0888-7543(90)90230-r]
Pronk, J. C., Frants, R. R., Jansen, W., Eriksson, A. W., Tonino, G. J. M. Evidence for duplication of the human salivary amylase gene. Hum. Genet. 60: 32-35, 1982. [PubMed: 6176528] [Full Text: https://doi.org/10.1007/BF00281260]
Roychoudhury, A. K., Nei, M. Human Polymorphic Genes: World Distribution. New York: Oxford Univ. Press (pub.) 1988.
Tricoli, J. V., Shows, T. B. Regional assignment of human amylase (AMY) to p22-p21 of chromosome 1. Somat. Cell Molec. Genet. 10: 205-210, 1984. [PubMed: 6608795] [Full Text: https://doi.org/10.1007/BF01534909]