Invertase

β-Fructofuranosidase is an enzyme that catalyzes the hydrolysis (breakdown) of the table sugar sucrose into fructose and glucose.[1][2] Alternative names for β-fructofuranosidase EC 3.2.1.26 include invertase, saccharase, glucosucrase, β-fructosidase, invertin, sucrase, fructosylinvertase, alkaline invertase, acid invertase, and the systematic name: β-fructofuranosidase. The resulting mixture of fructose and glucose is called inverted sugar syrup. Related to invertases are sucrases. Invertases and sucrases hydrolyze sucrose to give the same mixture of glucose and fructose. Invertase is a glycoprotein that hydrolyses (cleaves) the non-reducing terminal β-fructofuranoside residues. Invertases cleave the O-C(fructose) bond, whereas the sucrases cleave the O-C(glucose) bond.[3] Invertase cleaves the α-1,2-glycosidic bond of sucrose.

Invertase
Identifiers
EC no.3.2.1.26
CAS no.9001-57-4
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MetaCycmetabolic pathway
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For industrial use, invertase is usually derived from yeast. It is also synthesized by bees, which use it to make honey from nectar. Optimal temperature at which the rate of reaction is at its greatest is 60 °C and an optimum pH of 4.5. Typically, sugar is inverted with sulfuric acid.[3]

Invertase is produced by various organisms like yeast, fungi, bacteria, higher plants, and animals. For example: Saccharomyces cerevisiae, Saccharomyces carlsbergensis, S. pombe, Aspergillus spp, Penicillium chrysogenum, Azotobacter spp, Lactobacillus spp, Pseudomonas spp etc.

Applications and examples

Invertase is used to produce inverted sugar syrup.

Invertase is expensive, so it may be preferable to make fructose from glucose using glucose isomerase, instead. Chocolate-covered candies, other cordials, and fondant candies include invertase, which liquefies the sugar.[4]

Inhibition

Urea acts as a pure non-competitive inhibitor of invertase, presumably by breaking the intramolecular hydrogen bonds contributing to the tertiary structure of the enzyme.[5]

EC Number

Enzyme classification (EC) numbers are a way to organize all of the known enzymes in terms of how they function. In the instance of invertase, its EC number is 3.2.1.26. All enzymes with the first number being 3, are enzymes that are hydrolases. This indicates that this enzyme functions by breaking molecules apart with the addition of water. Having 3.2 as the first two numbers indicates that the hydrolase is acting on a sugar. The third number 1, further specifies that the enzyme hydrolases O- and S- glycosyl compounds. The final number specifies that the specific protein is invertase.

Structure and Function

Reaction Pathway

Invertase works to catalyze the cleavage of sucrose into its two monosaccharides, glucose and fructose.[6] This specific invertase (β-fructofuranosidase) cleaves the molecule from its fructose end resulting in the two monosaccharides. It does this by adding a hydrogen ion to the glycosidic atom by an imidazolium cation. From there, an unstable intermediate carbonium ion will be left behind by the leaving of an alcohol group. Finally, the nucleophilic oxygen atom from alcohol or water will attack the C-2 cation which will leave behind a fructose molecule. The active-site carboxylate anion will take action to help keep the unequal balance of electrons stabilized throughout this process.[7]

Purpose of Invertase in Yeast

As mentioned previously, invertase is commonly found in bakers' yeast. One of the main reasons that bakers use this yeast is to help bread rise, but another reason is to help influence the increase of sugar in bread. This function is able to happen due to the presence of invertase since glucose and fructose is sweeter than sucrose is.[8] When looking at invertase across different species of yeasts, it has been known to be more active in some more than others. The yeast that invertase is more active in is the yeast bakers use due to its higher sweetness levels.

Known Crystal Structures

Continuing to look at invertase through Saccharomyces, it can be seen that it has a unique structure; that structure being an octameric quaternary structure. Within the octameric quaternary structure, two dimerization types can be seen that in turn, form the octamer structure. Dimerization is an important aspect of protein folding due to it increasing the affinity of substrate binding. The crystal structure shows that the invertase is made up of eight subunits. The octamer shape is made up of two different types of dimers, a “‘closed’ arrangement” and an “‘open’ assembly” dimer. Each of these types has two subunits located opposite from each other in the structure. The “‘closed’ arrangement” dimers have fourteen out of the 32 hydrogen bonds made between the catalytic domain which creates a tighter pocket for the ligand; in turn, this makes it more stable. In contrast, the “‘open’ assembly” dimers only have a few hydrogen bonds in the catalytic domain, and the interactions that strengthen the pocket come from the salt bridges between Asp-45 and Lys-385. With the weaker interactions being in the “‘open’ assembly", it causes more instability that results in a lower denaturing temperature and lower durability at high-speed centrifugation. The way that the two dimers assemble, creates an antiparallel β sheet composed of β sandwiches made from two β sheets.[9]

Known Active Sites

While the focus has been on invertase in Saccharomyces, one of the known active sites is in the invertase in Bifidobacterium longum and is located within the β-propeller domain. The β-propeller domain is the inside the funnel created by five blades. Some amino acids to note are, Asp-54 and Glu-235, which are on the first strand of blades 1 and 4, along with Asn-53, Gln-70, Trp-78, Ser-114, Arg-180 and Asp-181 in the fructofuranoside ring.[10]

See also

References
  1. Myrbäck K (1960). "Invertases". In Boyer PD, Lardy H, Myrbäck K (eds.). The Enzymes. Vol. 4 (2nd ed.). New York: Academic Press. pp. 379–396.
  2. Neumann NP, Lampen JO (February 1967). "Purification and properties of yeast invertase". Biochemistry. 6 (2): 468–75. doi:10.1021/bi00854a015. PMID 4963242.
  3. Schiweck, Hubert; Clarke, Margaret; Pollach, Günter (2007). "Sugar". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a25_345.pub2. ISBN 978-3527306732.
  4. Kotwal, S. M.; Shankar, V. (2009). "Immobilized invertase". Biotechnol. Adv. 27 (4): 311–322. doi:10.1016/j.biotechadv.2009.01.009. PMID 19472508.
  5. Chase, Aurin M.; Von Meier, Hildegard C.; Menna, Vincent J. (February 1962). "The Non-Competitive Inhibition and Irreversible Inactivation of Yeast Invertase by Urea". Journal of Cellular and Comparative Physiology. 59 (1): 1–13. doi:10.1002/jcp.1030590102. ISSN 0095-9898. PMID 13878348.
  6. "Invertase - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2023-10-24.
  7. Kulshrestha, Samarth; Tyagi, Prasidhi; Sindhi, Vinita; Yadavilli, Kameshwar Sharma (2013-09-01). "Invertase and its applications – A brief review". Journal of Pharmacy Research. 7 (9): 792–797. doi:10.1016/j.jopr.2013.07.014. ISSN 0974-6943.
  8. Timmermans, Evelyne; Bautil, An; Brijs, Kristof; Scheirlinck, Ilse; Van der Meulen, Roel; Courtin, Christophe M. (2022-05-11). "Sugar Levels Determine Fermentation Dynamics during Yeast Pastry Making and Its Impact on Dough and Product Characteristics". Foods. 11 (10): 1388. doi:10.3390/foods11101388. ISSN 2304-8158. PMC 9140867. PMID 35626960.
  9. Sainz-Polo, M. Angela; Ramírez-Escudero, Mercedes; Lafraya, Alvaro; González, Beatriz; Marín-Navarro, Julia; Polaina, Julio; Sanz-Aparicio, Julia (2013-04-05). "Three-dimensional Structure of Saccharomyces Invertase". The Journal of Biological Chemistry. 288 (14): 9755–9766. doi:10.1074/jbc.M112.446435. ISSN 0021-9258. PMC 3617277. PMID 23430743.
  10. Bujacz, Anna; Jedrzejczak‐Krzepkowska, Marzena; Bielecki, Stanislaw; Redzynia, Izabela; Bujacz, Grzegorz (May 2011). "Crystal structures of the apo form of β‐fructofuranosidase from Bifidobacterium longum and its complex with fructose". The FEBS Journal. 278 (10): 1728–1744. doi:10.1111/j.1742-4658.2011.08098.x. ISSN 1742-464X.
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