Abstract
The action of branching enzyme (EC 2.4.l.l8) from Bacillus stearothermophilus on amylose was analyzed. The enzyme reduced the molecular size of amylose without increasing the reducing power. This result could not be explained by the normal branching reaction model. When the product was treated with glucoamylase (an exo++-type amylase), a resistant component remained. The glucoamylase-resistant component was easily digested by an endo-type alpha-amylase or by isoamylase plus glucoamylase. These results suggested that the glucoamylase-resistant component was a cyclic glucan composed of alpha-1,4- and alpha-l,6-glucosidic linkages. In other words, it was suggested that branching enzyme catalyzed cyclization of the alpha-l,4-glucan chain of the amylose molecule to form an alpha-l,6-glucosidic linkage, thereby forming two smaller molecules. Mass spectrometry also supported the cyclic nature of the product.
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Selected References
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- Borovsky D., Smith E. E., Whelan W. J., French D., Kikumoto S. The mechanism of Q-enzyme action and its influence on the structure of amylopectin. Arch Biochem Biophys. 1979 Dec;198(2):627–631. doi: 10.1016/0003-9861(79)90540-x. [DOI] [PubMed] [Google Scholar]
- Borovsky D., Smith E. E., Whelan W. J. On the mechanism of amylose branching by potato Q-enzyme. Eur J Biochem. 1976 Feb 16;62(2):307–312. doi: 10.1111/j.1432-1033.1976.tb10162.x. [DOI] [PubMed] [Google Scholar]
- Borovsky D., Smith E. E., Whelan W. J. Purification and properties of potato 1,4-alpha-D-glucan:1,4-alpha-D-glucan 6-alpha-(1,4-alpha-glucano)-transferase. Evidence against a dual catalytic function in amylose-branching enzyme. Eur J Biochem. 1975 Nov 15;59(2):615–625. doi: 10.1111/j.1432-1033.1975.tb02490.x. [DOI] [PubMed] [Google Scholar]
- Borovsky D., Smith E. E., Whelan W. J. Temperature-independence of the action of Q-enzyme and the nature of the substrate for Q-enzyme. FEBS Lett. 1975 Jun 15;54(2):201–205. doi: 10.1016/0014-5793(75)80074-3. [DOI] [PubMed] [Google Scholar]
- Jespersen H. M., MacGregor E. A., Henrissat B., Sierks M. R., Svensson B. Starch- and glycogen-debranching and branching enzymes: prediction of structural features of the catalytic (beta/alpha)8-barrel domain and evolutionary relationship to other amylolytic enzymes. J Protein Chem. 1993 Dec;12(6):791–805. doi: 10.1007/BF01024938. [DOI] [PubMed] [Google Scholar]
- Preiss J. Bacterial glycogen synthesis and its regulation. Annu Rev Microbiol. 1984;38:419–458. doi: 10.1146/annurev.mi.38.100184.002223. [DOI] [PubMed] [Google Scholar]
- Takata H., Kuriki T., Okada S., Takesada Y., Iizuka M., Minamiura N., Imanaka T. Action of neopullulanase. Neopullulanase catalyzes both hydrolysis and transglycosylation at alpha-(1----4)- and alpha-(1----6)-glucosidic linkages. J Biol Chem. 1992 Sep 15;267(26):18447–18452. [PubMed] [Google Scholar]
- Takata H., Takaha T., Kuriki T., Okada S., Takagi M., Imanaka T. Properties and active center of the thermostable branching enzyme from Bacillus stearothermophilus. Appl Environ Microbiol. 1994 Sep;60(9):3096–3104. doi: 10.1128/aem.60.9.3096-3104.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]