Carbohydrate-modifying enzymes

They are typically polar, have low binding affinities, and often lack specificity (i.e., they interact with many related lectins). Moreover, even with advances in carbohydrate synthesis, it is difficult to rapidly assemble oligosaccharide derivatives to optimize their potency. These challenges are also apparent in the efforts to block carbohydrate-modifying enzymes. 

An alternative approach for treating bacterial infections has seen the development of carbohydrate based antibiotics to target carbohydrate receptors and carbohydrate modifying enzymes [6]. 

Starch and other carbohydrate-modifying enzymes hold the second place in world enzyme production behind detergent enz3ones. 

Hydrazide groups can react with carbonyl groups to form stable hydrazone linkages. Derivatives of proteins formed from the reaction of their carboxylate side chains with adipic acid dihydrazide (Chapter 4, Section 8.1) and the water-soluble carbodiimide EDC (Chapter 3, Section 1.1) create activated proteins that can covalently bind to formyl residues. Hydrazide-modified enzymes prepared in this manner can bind specifically to aldehyde groups formed by mild periodate oxidation of carbohydrates (Chapter 1, Section 4.4). These reagents can be used in assay systems to detect or measure glycoproteins in cells, tissue sections, or blots (Gershoni et al., 1985). 

Since from physiological studies it was evident that increased carbohydrate levels are able to confer resistance to cold, it is surprising that none of the cloned transcripts can so far be related to carbohydrate metabolism. One explanation for this may be that low temperature activates or modifies enzymes which are involved in metabolism at normal temperatures, and therefore transcripts for these enzymes would not... 

A role for the carbohydrate moieties in the catalytic process of an enzyme was suggested many years ago.24 However, studies with several different enzymes19,149,150 have shown that enzymic activity is affected only slightly if the carbohydrate residues are oxidized with periodate. Furthermore, removal of carbohydrate residues with gly-cosidases,1,15 followed by measurements of activity, has shown that the resulting, modified enzymes had specific activities that were essentially unchanged. With ribonuclease B, it has also been con-... 

The properties of 3-D-fructofuranosidase (invertase) of Saccharomyces cerevisiae, and of the modified enzyme after removal of about 90% of the carbohydrate residues, have been found to differ considerably, not only in stability but also in their capacity to be renatured following inactivation by guanidinium chloride. The covalently bound carbohydrate of yeast 3-D-fructo-... 

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. 

Analysis of amylodextrins is of vital importance to the researcher investigating activity mechanisms of carbohydrate degrading enzymes and to the researcher undertaking structural studies of unmodified and modified polysaccharides and the carbohydrate moiety of proteoglycans and glycoproteins. Structural characterization of amylodextrins produced after starch hydrolysis by newly discovered/created carbohydrolases helps in studies regarding their activity patterns and specificity structures of novel polysacharides, etc. 

Ketose chemistry is, by far, not as advanced as the knowledge on aldose reactions and conversions and, consequently, the application of isomerases in this area will be an important contribution to open up this fascinating and underrated field of carbohydrate chemistry. Rare and potentially interesting aldoses, on the other hand, which have been resistant to conventional chemical means of access, can today be made available with a range of enzymatically catalysed reactions employing sugar modifying enzymes such as the ones under consideration in this account. 

Glucoamylases.—Although the molecular weight and the carbohydrate content of Aspergillus awamori glucoamylase were reduced on treatment with subtilisin, most of the enzymic activity was retained. The modified enzyme was less stable and its ability to hydrolyse starch was diminished. 

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