Heptose Explained
A heptose is a monosaccharide with seven carbon atoms.
They have either an aldehyde functional group in position 1 (aldoheptoses) or a ketone functional group in position 2, 3 or 4 (ketoheptoses). Ketoheptoses have 4 chiral centers, whereas aldoheptoses have 5.
Examples
There are few examples of seven-carbon sugars in nature, among which are:
Structural role
The production of heptose is conserved across gram-negative bacteria. In the form of L-glycero-D-mannose-heptose, heptose is a key component in the secondary membrane of gram-negative bacteria. Gram-negative bacteria, in addition to having a cell wall, are also encapsulated by a membrane composed of lipopolysaccharides.[5] These lipopolysaccharides comprise an endotoxin that acts as an immune system agonist and elicits strong responses. This toxin, known as lipid A, consists of a core of one to three heptose molecules. The 7-carbon heptose molecules are essential for stability in the lipopolysaccharide membrane, forming an interconnected network utilizing divalent cations.
Role in cell signaling
Heptose, in the form of heptose 1-7-bisphosphate, has been found to be one of the components responsible for the pathogenic nature of gram negative bacteria. In the bacterium biosynthesis pathway, heptose is phosphorylated to heptose 1-7-bisphosphate. In addition, like other sugars, heptose may exist in either the alpha anomer or the beta anomer. Before synthetic production of heptose-bisphosphate (HBP) for studies, cytosolic HBP was thought to influence NF-kB, a transcription factor in mammalian cells.[6] Along with producing the first synthetic version of HBP, it was shown that the beta form of the heptose acts as a pathogen-associated molecular pattern (PAMP) and activates the NF-kB signaling pathway. A PAMP is a specific structure, component, or molecule that triggers the immune response after recognition by pattern recognition receptors on mammalian cells.
Notes and References
- 10.1021/ja01104a532. Transaldolase: The Formation of Fructose-6-Phosphate from Sedoheptulose-7-Phosphate. Journal of the American Chemical Society. 75. 8. 2021. 1953. Horecker. B. L. Smyrniotis. P. Z. 1953JAChS..75.2021H.
- 10.1016/j.tibs.2014.06.005 . 25037503 . The pentose phosphate pathway and cancer . Trends in Biochemical Sciences . 39 . 8 . 347–354 . 2014 . Patra . Krushna C . Hay . Nissim . 4329227.
- Liu . Xuan . Sievert . James . Arpaia . Mary Lu . Madore . Monica A. . Postulated Physiological Roles of the Seven-carbon Sugars, Mannoheptulose, and Perseitol in Avocado . Journal of the American Society for Horticultural Science . 2002-01-01 . 127 . 1 . 108–114 . 2018-06-26 . en . 10.21273/JASHS.127.1.108 . free . subscription .
- Taylor . Patricia L. . Blakely . Kim M. . de Leon . Gladys P. . Walker . John R. . McArthur . Fiona . Evdokimova . Elena . Zhang . Kun . Valvano . Miguel A. . Wright . Gerard D. . Junop . Murray S. . 1 February 2008 . Structure and Function of Sedoheptulose-7-phosphate Isomerase, a Critical Enzyme for Lipopolysaccharide Biosynthesis and a Target for Antibiotic Adjuvants . Journal of Biological Chemistry . en . 283 . 5 . 2835–2845 . 10.1074/jbc.M706163200. free . 18056714 .
- Gaudet . Ryan G. . Gray-Owen . Scott D. . 2016-09-22 . Heptose Sounds the Alarm: Innate Sensing of a Bacterial Sugar Stimulates Immunity . PLOS Pathogens . en . 12 . 9 . e1005807 . 10.1371/journal.ppat.1005807 . free . 1553-7374 . 5033458 . 27658039.
- Inuki . Shinsuke . Aiba . Toshihiko . Kawakami . Shota . Akiyama . Taishin . Inoue . Jun-ichiro . Fujimoto . Yukari . 2017-06-16 . Chemical Synthesis of d - glycero - d - manno -Heptose 1,7-Bisphosphate and Evaluation of Its Ability to Modulate NF-κB Activation . Organic Letters . en . 19 . 12 . 3079–3082 . 10.1021/acs.orglett.7b01158 . 28541700 . 1523-7060. subscription .
