Fuculose

l-Fuculose

Names
IUPAC name 6-Deoxy-l-tagatose
Systematic IUPAC name (3R,4S,5S)-2-(Hydroxymethyl)-5-methyltetrahydrofuran-2,3,4-triol
Identifiers
CAS Number	13074-08-3^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17617
ChemSpider	9621375
KEGG	C01721
PubChem CID	6857362
CompTox Dashboard (EPA)	DTXSID30926880
InChI InChI=1S/C6H12O5/c1-3(8)5(10)6(11)4(9)2-7/h3,5-8,10-11H,2H2,1H3/t3-,5+,6-/m0/s1 Key: QZNPNKJXABGCRC-LFRDXLMFSA-N
SMILES O[C@H]1[C@@H](O)C(O)(CO)O[C@H]1C
Properties
Chemical formula	C6H12O5
Molar mass	164.16 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

Fuculose or 6-deoxy-tagatose is a ketohexose deoxy sugar.^[1][2] Fuculose is involved in the process of sugar metabolism.^[3] l-Fuculose can be formed from l-fucose by l-fucose isomerase and converted to L-fuculose-1-phosphate by l-fuculose kinase.^[4]

L-Fuculose

L-fuculose is a ketohexose deoxy sugar with many beneficial uses in treating various diseases, such as HIV, Hepatitis B, fucosidosis, etc.^[5] and is overall very sought out after due to its agricultural and pharmaceutical value. However, L-fuculose is very rare and can be difficult to obtain.^[5] Although it may be hard to obtain naturally, there are many methods that allow people to access this useful reaction intermediate from enzymatic processes. L-fuculose is often used as an intermediate from other sugars to form its aldose isomer form, L-fucose. L-fucose kinase can phosphorylate the L-fuculose intermediate to get L-fucose-1-phosphate that can be used for further reactions^[5].

Isolation and Characterization

In 1953, Seymour S. Cohen figured out that an adapted strain (Ba15) of Escherichia Coli converted the L-fucose substrate to a ketose, which was determined by the cysteine-carbazole reaction.^[6] The cysteine-carbazole reaction is a colorimetric assay that can determine sugar specificity, whether it is an aldose or a ketose. This reaction was based on the color intensity given off after reacting to the cysteine and carbazole for a specific determination of the sugar. The standard used to compare was L-fuculose o-nitro-phenylhydrazone that produced the same color intensity, with fucose giving a small percentage of the intensity of the color produced by the ketose sugar.^[6] The L-fuculose o-nitro-phenylhydrazone produced a high intensity color and is the derivative of L-fuculose. L-fuculose also had produced this high intensity color, while the aldose form, L-fucose, produced a very low intensity color. When comparing both of these isomers to the standard, it was clear that the product that also produced an intense color formation was the ketose sugar, L-fuculose.

Formation

As mentioned previously, L-fucose isomerase can interconvert between the two isomers L-fucose and L-fuculose. Both forms have their own unique advantages for industrial applications, but L-fucose can often be used as a substrate to form more molecules of L-fuculose for the intended purpose. The L-fucose is an aldohexose deoxy sugar and it has an aldehyde on the first carbon, while L-fuculose is a ketohexose deoxy sugar with a ketone on the second carbon on the carbon chain. In order for L-fucose isomerase to interconvert between L-fucose and L-fuculose, it requires cofactors, such as the divalent cations Mn2+ and Co2+.^[7] To test if the isomerase reacts to both L-fucose and L-fuculose to interconvert, paper chromatography can be used to prove this. The fucose showed to have an Rf value of 0.35 showing as a brown spot, while fuculose had an Rf value of 0.50, showing as a yellow spot.^[6] Both sugars showing as products shows how the FucI can interconvert between the aldose and ketose form. Since the isomerase can interconvert between both of the ketose and aldose forms, they both are the substrates. However, specific isomerases can favor one substrate over the other, causing one sugar formation to be favored over the other. In the species Raoultella, L-fucose isomerase (RdFucI) was found and it was shown that this isomerase exhibited higher enzymatic activity for L-fuculose as the substrate compared to L-fucose, meaning the reverse reaction was favored.^[7] While L-fuculose can still be produced as a product from, it was faster for the formation of L-fucose.

See also

• l-fuculose-phosphate aldolase
• l-fuculosekinase

References

1. Lindhorst TK (2007). Essentials of Carbohydrate Chemistry and Biochemistry (1 ed.). Wiley-VCH. ISBN 978-3-527-31528-4.
2. Robyt JF (1997). Essentials of Carbohydrate Chemistry (1st ed.). Springer. ISBN 0-387-94951-8.
3. Wen L, Zang L, Huang K, Li S, Wang R, Wang PG (February 2016). "Efficient enzymatic synthesis of L-rhamnulose and L-fuculose". Bioorganic & Medicinal Chemistry Letters. 26 (3): 969–972. doi:10.1016/j.bmcl.2015.12.051. PMC 5984655. PMID 26778148.
4. Iqbal, Muhammad Waheed; et al. (2021). "A review on selective l-fucose/d-arabinose isomerases for biocatalytic production of l-fuculose/d-ribulose". International Journal of Biological Macromolecules. 168: 558–571. doi:10.1016/j.ijbiomac.2020.12.021. PMID 33296692. S2CID 228088451.
5. Journal of Applied Microbiology. Oxford University Press (OUP).
6. Journal of Biological Chemistry. Elsevier BV. doi:10.1074/jbc.
7. Kim, In Jung; Kim, Do Hyoung; Nam, Ki Hyun; Kim, Kyoung Heon (December 2019). "Enzymatic synthesis of l-fucose from l-fuculose using a fucose isomerase from Raoultella sp. and the biochemical and structural analyses of the enzyme". Biotechnology for Biofuels. 12 (1) 282. Bibcode:2019BB.....12..282K. doi:10.1186/s13068-019-1619-0. ISSN 1754-6834. PMC 6894278. PMID 31827610.