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Pathway Description
Galactose Metabolism
Mus musculus
Category:
Metabolite Pathway
Sub-Category:
Metabolic
Created: 2018-01-21
Last Updated: 2019-09-12
This pathway depicts the conversion of galactose into glucose, lactose, and other sugar intermediates that may be used for a range of metabolic process.
Dietary sources of galactose are numerous, but some of the primary sources in the human diet can be found in milk and milk derivative products.
This is because during digestion milk sugars and lactose are hydrolyzed into their molecular constituents (e.g. base monosaccharides). In milk, such monosaccharides include glucose and galactose.
The metabolism of the sugar Galactose is occurs almost entirely in the liver, and its metabolism is the consequence of three steps or reactions. First, the phosphorylation of galactose is induced by a special enzyme with the predictable name, galactokinase, and produces galactose 1-phosphate. Second, this biproduct and a second molecule, UDP-glucose, undergo a reaction which leads to the formation of UDP-galactose and glucose 1-phosphate. Thus, this reaction produces 1 molecule of glucose 1-phosphate per molecule of galactose.
This is mediated by the enzyme galactose-1-phosphate uridylyltransferase (GALT). The resulting UDP-galactose undergoes epimerization to form UDP-glucose via the enzyme UDP-galactose-4 epimerase (GALE). The UDP-glucose can be used in glucuronidation reactions and other pentose interconversions. In a reaction shared with other pathways, glucose 1-phosphate can be converted into glucose 6-phosphate. There are other pathways associated with galactose metabolism. For instance, galactose can be converted into UDP-glucose by the sequential activities of GALK, UDP-glucose pyrophosphorylase 2 (UGP2), and GALE. Galactose can also be reduced to galactitol by NADPH-dependent aldose reductase. Also shown in this pathway is
the conversion of glucose to galactose vis a vis a different process to the ones described earlier. This pathway, called hexoneogenesis, allows mammary glands to produce galactose. It should be noted however, that despite the existence of this pathway of galactose production, the vast majority of galactose in breast milk is actually the result of direct uptake up from the blood, whereas only a small fraction, ~35%, is the result of this de novo process hexoneogenesis.
Also depicted in this pathway are the conversions of other dietary di and tri-saccharides (raffinose, manninotriose, melibiose, stachyose) into galactose, glucose and fructose as well as and dietary sugar alcohols (melibitol, galactinol, galactosylglycerol) into sorbitol, myo-inositol, and glycerol.
References
Galactose Metabolism References
Lehninger, A.L. Lehninger principles of biochemistry (4th ed.) (2005). New York: W.H Freeman.
Salway, J.G. Metabolism at a glance (3rd ed.) (2004). Alden, Mass.: Blackwell Pub.
Wang AM, Ioannou YA, Zeidner KM, Desnick RJ: Murine alpha-N-acetylgalactosaminidase: isolation and expression of a full-length cDNA and genomic organization: further evidence of an alpha-galactosidase gene family. Mol Genet Metab. 1998 Oct;65(2):165-73. doi: 10.1006/mgme.1998.2750.
Pubmed: 9787108
Herrmann T, Schindler D, Tabe H, Onodera O, Igarashi S, Polack A, Zehnpfennig D, Shoji Tsuji: Molecular cloning, structural organization, sequence, chromosomal assignment, and expression of the mouse alpha-N-acetylgalactosaminidase gene. Gene. 1998 May 12;211(2):205-14. doi: 10.1016/s0378-1119(98)00103-6.
Pubmed: 9602128
Ehringer MA, Thompson J, Conroy O, Xu Y, Yang F, Canniff J, Beeson M, Gordon L, Bennett B, Johnson TE, Sikela JM: High-throughput sequence identification of gene coding variants within alcohol-related QTLs. Mamm Genome. 2001 Aug;12(8):657-63.
Pubmed: 11471062
Carninci P, Kasukawa T, Katayama S, Gough J, Frith MC, Maeda N, Oyama R, Ravasi T, Lenhard B, Wells C, Kodzius R, Shimokawa K, Bajic VB, Brenner SE, Batalov S, Forrest AR, Zavolan M, Davis MJ, Wilming LG, Aidinis V, Allen JE, Ambesi-Impiombato A, Apweiler R, Aturaliya RN, Bailey TL, Bansal M, Baxter L, Beisel KW, Bersano T, Bono H, Chalk AM, Chiu KP, Choudhary V, Christoffels A, Clutterbuck DR, Crowe ML, Dalla E, Dalrymple BP, de Bono B, Della Gatta G, di Bernardo D, Down T, Engstrom P, Fagiolini M, Faulkner G, Fletcher CF, Fukushima T, Furuno M, Futaki S, Gariboldi M, Georgii-Hemming P, Gingeras TR, Gojobori T, Green RE, Gustincich S, Harbers M, Hayashi Y, Hensch TK, Hirokawa N, Hill D, Huminiecki L, Iacono M, Ikeo K, Iwama A, Ishikawa T, Jakt M, Kanapin A, Katoh M, Kawasawa Y, Kelso J, Kitamura H, Kitano H, Kollias G, Krishnan SP, Kruger A, Kummerfeld SK, Kurochkin IV, Lareau LF, Lazarevic D, Lipovich L, Liu J, Liuni S, McWilliam S, Madan Babu M, Madera M, Marchionni L, Matsuda H, Matsuzawa S, Miki H, Mignone F, Miyake S, Morris K, Mottagui-Tabar S, Mulder N, Nakano N, Nakauchi H, Ng P, Nilsson R, Nishiguchi S, Nishikawa S, Nori F, Ohara O, Okazaki Y, Orlando V, Pang KC, Pavan WJ, Pavesi G, Pesole G, Petrovsky N, Piazza S, Reed J, Reid JF, Ring BZ, Ringwald M, Rost B, Ruan Y, Salzberg SL, Sandelin A, Schneider C, Schonbach C, Sekiguchi K, Semple CA, Seno S, Sessa L, Sheng Y, Shibata Y, Shimada H, Shimada K, Silva D, Sinclair B, Sperling S, Stupka E, Sugiura K, Sultana R, Takenaka Y, Taki K, Tammoja K, Tan SL, Tang S, Taylor MS, Tegner J, Teichmann SA, Ueda HR, van Nimwegen E, Verardo R, Wei CL, Yagi K, Yamanishi H, Zabarovsky E, Zhu S, Zimmer A, Hide W, Bult C, Grimmond SM, Teasdale RD, Liu ET, Brusic V, Quackenbush J, Wahlestedt C, Mattick JS, Hume DA, Kai C, Sasaki D, Tomaru Y, Fukuda S, Kanamori-Katayama M, Suzuki M, Aoki J, Arakawa T, Iida J, Imamura K, Itoh M, Kato T, Kawaji H, Kawagashira N, Kawashima T, Kojima M, Kondo S, Konno H, Nakano K, Ninomiya N, Nishio T, Okada M, Plessy C, Shibata K, Shiraki T, Suzuki S, Tagami M, Waki K, Watahiki A, Okamura-Oho Y, Suzuki H, Kawai J, Hayashizaki Y: The transcriptional landscape of the mammalian genome. Science. 2005 Sep 2;309(5740):1559-63. doi: 10.1126/science.1112014.
Pubmed: 16141072
Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J: The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome Res. 2004 Oct;14(10B):2121-7. doi: 10.1101/gr.2596504.
Pubmed: 15489334
Wollscheid B, Bausch-Fluck D, Henderson C, O'Brien R, Bibel M, Schiess R, Aebersold R, Watts JD: Mass-spectrometric identification and relative quantification of N-linked cell surface glycoproteins. Nat Biotechnol. 2009 Apr;27(4):378-86. doi: 10.1038/nbt.1532. Epub 2009 Apr 6.
Pubmed: 19349973
This pathway was propagated using PathWhiz -
Pon, A. et al. Pathways with PathWhiz (2015) Nucleic Acids Res. 43(Web Server issue): W552–W559.
Propagated from SMP0000043
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