Where cyclodextrins can be found in the nature and what is the purpose of cyclodextrins in the nature?

The enzyme cyclodextrin glucanotransferase (CGTase) converts linear glucan structure in an intramolecular transglycosylation reacton (cyclization) into cyclodextrins (CD). Genes encoding for CGTases were identified and isolated from various organisms belonging to the domain of bacteria or archaea. These microbes are widely spread among terrestrial and aquatic environments. Especially, the genus Bacillus includes generic CGTase producers. Compost piles and soils are good spots to search for such strains. They secrete CGTase into the medium, while putative ABC transporters can take up the CD into the cells. Intracellular cyclodextrinase or maltogenic amylase splits CD into monomers to enable their utilization as carbon and energy source [1–3]. Therefore, these strains probably secrete CGTase to pack, store and, thereby, protect the glucan substrate from biotic or abiotic degradation. In this context, CD cannot be degraded by exo-acting amylases. They further act as amylase inhibitors and might therefore
disadvantage other strains regarding the competition for nutrients [4,5].

1. Park K-H, Kim T-J, Cheong T-K, Kim J-W, Oh B-H & Svensson B (2000). Structure, specificity and
   function of cyclomaltodextrinase, a multispecific enzyme of the α-amylase family. Biochim. Biophys.
   Acta, Protein Struct. Mol. Enzymol. 1478, 165–185.
2. Fiedler G, Pajatsch M & Böck A (1996). Genetics of a novel starch utilisation pathway present in
   Klebsiella oxytoca. J. Mol. Biol. 256, 279–291.
3. Hashimoto Y, Yamamoto T, Fujiwara S, Takagi M & Imanaka T (2001). Extracellular synthesis,
   specific recognition, and intracellular degradation of cyclomaltodextrins by the hyperthermophilic
   archaeon Thermococcus sp. strain B1001. J. Bacteriol. 183, 5050–5057.
4. Hamilton, Kelly & Fogarty (2000). Review: cyclodextrins and their interaction with amylolytic
   enzymes. Enzyme Microb. Technol. 26, 561–567.
5. Fukuda K, Teramoto Y, Goto M, Sakamoto J, Mitsuiki S & Hayashida S (1992). Specific inhibition
   by cyclodextrins of raw starch digestion by fungal glucoamylase. Biosci. Biotechnol. Biochem. 56,
   556–559.