Starch-debranching enzymes

A starch-debranching isoamylase, obtained from sugary 1 (sul) maize, has been cloned by James et al.70 and found to have 32% sequence identity with Pseudomonas isoamylase. Other isoamylases or starch debranching enzymes have been isolated from Cytophaga sp.,71 Streptomyces sp.,72 Flavobacterium sp.,73 a yeast, Lipomyces kononenkoae,74 potato tubers,75 B. circulans76 and an alkaline isoamylase with a pH optimum of 9 from an alkalophilic Bacillus sp.77... 

Branched cydodextrins are also used to increase the solubility of complexes. Two methods are used to make branched cydodextrins, an enzymic method and a pyrolytic method. In the enzymic method, a starch debranching enzyme, such as pul-lulanase, is added to a solution of cyclodextrin and a large excess of D-glucose or maltose to force the reaction to proceed in the reverse direction, i.e. to add rather than remove a branch.69 Since the equilibrium favors the debranching reaction, yields are low and the product typically contains —15% branched cyclodextrin and —85% glucose or maltose. Purification is difficult because of the high solubility of both the glucose or maltose and the branched cyclodextrin, but much of the unreacted cyclodextrin can be removed by crystallization. 

Dohlert, D. C., and Knutson, C. A. 1991. Two classes of starch debranching enzymes from developing maize kernels. J. Plant Physiol. 138, 566-572. 

Manners, D. J. 1997. Observations on the specificity and nomenclature of starch debranching enzymes. J. Appl. Glycosci. 44, 83-85. 

Nakamura, Y., Umemoto, T., Ogata, N., Kuboki, Y., Yano, M., and Saski, T. 1996a. Starch debranching enzyme (R-enzyme or pullulanase) from developing rice endosperm Purification, cDNA and chromosomal localization of the gene. Planta 199, 203-218. 

Nakamura, Y.. Umemoto, T., Takahata, Y., Komae, K., Amano, E., and Satoh, H. 19%b. Changes in structure of starch and enzyme activities affected by sugary mutation in developing rice endosperm Possible role of starch debranching enzyme in amylopectin biosynthesis. Physiol. Plant. 

Alpha-dextrin endo-1,6-alpha-glucosidase. Pullulanase. Pullulan 6-glucanohydrolase. Limit dextrinase. Debranching enzyme. 3.2.1.41 Starch-debranching enzyme, hydrolyses (l-6)-alpha-glucosidic linkages in pullulan and starch to form maltotriose. 

FRANCISCO, P.B., ZHANG, Y., PARK, S.Y., OGATA, N., YAMANOUCHI, H., NAKAMURA, Y., Genomic DNA sequence of a rice gene coding for a pullulanase-type of starch debranching enzyme, Biochim. Biophys. Acta, 1998, 1387,469-477. 

Similar separation behavior emerges in the case of debranching enzyme such as puUulanase, and the interaction occurring here is also at the active sites of such enzymes. For example, the starch-debranching enzymes from spinach leaf is loaded in /3-CD Sepharose 6B and washed with sodium acetate buffer to remove other enzymes, then the retarded starch-debranching enzyme is released with the elution solution including fS-CD. Actually, /3-CD exhibit affinity for all types of... 

Starch-Modifying Enzymes Starch is one of the most abundant carbohydrates in terrestrial plants and the most important polysaccharide used by humankind. This polymer is normally processed and used in a variety of products such as starch hydrolysates, starch or maltodextrin derivatives, fructose, glucose syrups, and cyclodextrins [148, 149]. In addition, starch is widely used as a raw material in the paper industry, in polyol production, and as economic substrate for many microbial fermentations [149]. Starch consists of a large number of glucose units that can be linearly attached as hehcal amylose [ 99% a-(l-4) and 1% a-(l-6) bonds] or branched as amylopectin [ 95% a-(l-4) and 5% a-(l-6) bonds] [69]. In nature, four types of starch-converting enzymes exist (i) endoamylases (ii) exoamylases (iii) debranching enzymes and (iv) transferases. 

P-amylase, and debranching enzymes. Conversion of D-glucose to D-fmctose is mediated by glucose isomerase, mosdy in its immobilized form in columns. Enzymic degradation of starch to symps has been well reviewed (116—118), and enzymic isomerization, especially by immobilized glucose isomerase, has been fiiUy described (119) (see Syrups). 

Guraya, H. S., James, C., Champagne, E. T. (2001). Effect of enzyme concentration and storage temperature on the formation of slowly digestible starch from cooked debranched rice starch. Starch/Starke, 53, 131-139. 

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