Cycloamylose
Cycloamyloses are cyclic α-1,4 linked glucans comprising dozens or hundreds of glucose units. Chemically they are similar to the much smaller cyclodextrins, which are typically composed of 6, 7 or 8 glucose units.
Discovery[edit]
Cycloamyloses were discovered as a result of studies of the function of 4-α-glucanotransferase, also known as disproportionating enzyme or D-enzyme (EC 2.4.1.25) isolated from potato.[1]
Synthesis[edit]
Upon incubation of D-enzyme with high molecular weight amylose, a product was obtained with decreased ability to form a blue complex with iodine, without reducing or non-reducing ends, and resistant to hydrolysis by glucoamylase (an exoamylase). Takaha and Smith deduced that the product was a cyclic polymer, which they confirmed by mass spectrometry and acid hydrolysis, and showed that it comprised between 17 and several hundred glucose units.[2] It was subsequently shown that D-enzyme could create complex cycloglucans from amylopectin.[3] Similar 4-α-glucanotransferases from bacteria and other organisms have also been shown to produce cycloglucans upon incubation with amylose or amylopectin.
Structure[edit]
While the structures of cyclodextrins are planar circles, the structure of cycloamyloses with 10 to 14 glucose units were determined to be circular with strain-induced band-flips and kinks.[4][5] In contrast the structure of a larger cycloamylose with 26 glucose units was determined to comprise two short left-handed V-amylose helices in antiparallel arrangement.[6][7]
Applications[edit]
Cycloamyloses contain cavities in the helices which are capable of accommodating guest molecules, which suggested applications in chemical technologies.[8] Cycloamylose is used in artificial chaperone technology for the refolding of denatured proteins. Cycloglucans have physicochemical properties that make them useful in food and manufacturing.
References[edit]
- ^ Takaha, T.; Yanase, M.; Okada, S.; Smith, S. M. (1993-01-15). "Disproportionating enzyme (4-alpha-glucanotransferase; EC 2.4.1.25) of potato. Purification, molecular cloning, and potential role in starch metabolism". Journal of Biological Chemistry. 268 (2): 1391–1396. doi:10.1016/S0021-9258(18)54088-6. ISSN 0021-9258. PMID 7678257.
- ^ Takaha, Takeshi; Yanase, Michiyo; Takata, Hiroki; Okada, Shigetaka; Smith, Steven M. (1996-02-09). "Potato D-enzyme Catalyzes the Cyclization of Amylose to Produce Cycloamylose, a Novel Cyclic Glucan". Journal of Biological Chemistry. 271 (6): 2902–2908. doi:10.1074/jbc.271.6.2902. ISSN 0021-9258. PMID 8621678.
- ^ Takaha, Takeshi; Yanase, Michiyo; Takata, Hiroki; Okada, Shigetaka; Smith, Steven M. (1998-06-18). "Cyclic Glucans Produced by the Intramolecular Transglycosylation Activity of Potato D-Enzyme on Amylopectin". Biochemical and Biophysical Research Communications. 247 (2): 493–497. doi:10.1006/bbrc.1998.8817. PMID 9642157.
- ^ Jacob, Joël; Geßler, Katrin; Hoffmann, Daniel; Sanbe, Haruyo; Koizumi, Kyoko; Smith, Steven M.; Takaha, Takeshi; Saenger, Wolfram (1998-03-16). "Strain-Induced "Band Flips" in Cyclodecaamylose and Higher Homologues". Angewandte Chemie International Edition. 37 (5): 605–609. doi:10.1002/(sici)1521-3773(19980316)37:5<605::aid-anie605>3.0.co;2-c. ISSN 1521-3773. PMC 1147477. PMID 3827863.
- ^ Jacob, Joël; Geβler, Katrin; Hoffmann, Daniel; Sanbe, Haruyo; Koizumi, Kyoko; Smith, Steven M; Takaha, Takeshi; Saenger, Wolfram (1999-12-12). "Band-flip and kink as novel structural motifs in α-(1→4)-d-glucose oligosaccharides. Crystal structures of cyclodeca- and cyclotetradecaamylose". Carbohydrate Research. 322 (3–4): 228–246. doi:10.1016/S0008-6215(99)00216-5.
- ^ Saenger, Wolfram; Jacob, Joël; Gessler, Katrin; Steiner, Thomas; Hoffmann, Daniel; Sanbe, Haruyo; Koizumi, Kyoko; Smith, Steven M.; Takaha, Takeshi (1998-01-01). "Structures of the Common Cyclodextrins and Their Larger AnaloguesBeyond the Doughnut". Chemical Reviews. 98 (5): 1787–1802. doi:10.1021/cr9700181. PMID 11848949.
- ^ Gessler, Katrin; Usón, Isabel; Takaha, Takeshi; Krauss, Norbert; Smith, Steven M.; Okada, Shigetaka; Sheldrick, George M.; Saenger, Wolfram (1999-04-13). "V-Amylose at atomic resolution: X-ray structure of a cycloamylose with 26 glucose residues (cyclomaltohexaicosaose)". Proceedings of the National Academy of Sciences. 96 (8): 4246–4251. Bibcode:1999PNAS...96.4246G. doi:10.1073/pnas.96.8.4246. ISSN 0027-8424. PMC 16317. PMID 10200247.
- ^ Takaha, Takeshi; Smith, Steven M. (1999-01-01). "The Functions of 4-α-glucanotransferases and their use for the Production of Cyclic Glucans". Biotechnology and Genetic Engineering Reviews. 16 (1): 257–280. doi:10.1080/02648725.1999.10647978. PMID 10819082.