Isomaltose hydrolysis

The hydrolysis of starch by salivary and pancreatic amylases catalyze random hydrolysis of a(l—>4) glycoside bonds, yielding dextrins, then a mixmre of glucose, maltose, and isomaltose (from the branch points in amylopectin). 

This enzyme [EC 3.2.1.10] (also referred to as oUgo-1,6-glucosidase, sucrase-isomaltase, and limit dextrinase) catalyzes the hydrolysis of l,6-o -D-glucosidic linkages in isomaltose and dextrin products generated from starch and glycogen via a-amylase. See also Sucrase... 

This enzyme [EC 3.2.1.57] catalyzes the hydrolysis of pullulan to produce isopanose (6-a-maltosylglucose). Panose (4-o -isomaltosylglucose) is a substrate and is hydrolyzed to isomaltose and glucose. 

Further findings relevant for the establishment of the chemical nature of enzymatic catalysis and technical apphcation followed within rather short time. Croft-Hill performed the first enzymatic synthesis, that of isomaltose, in 1898, allowing a yeast extract (df-glycosidase) to act on 40% glucose solution (Sumner and Somers, 1953). In 1900 Kastle and Loevenhart found that the hydrolysis of fat and other esters by lipases is a reversible reaction and that enzymatic synthesis can occur in a dilute mixture of alcohol and acid (Sumner and Myiback 1950). This principle was utilized for the synthesis of... 

Oligo-( 1— 6)-D-glucosidase isomaltase, dextrin 6-a-D-glucanohydrolase hydrolysis of (1— -6)-a-D-glucosyl links in isomaltose, panose, and gluco-oligosaccharides produced from starch by alpha amylase... 

Figure 2 (78) illustrates the correspondence found for the first time between condensation and hydrolysis for these glucoamylase-catalyzed reactions. Most important is that the condensations of /3-D-glucopyranose to maltose and isomaltose involve configurational inversion from which we infer that the glucosylic bond is split and the D-glucopyranosyl group transferred. 

Other disaccharides are the product of the breakdown of larger polysaccharides. Maltose, cellobiose, and isomaltose are all composed of glucose residues (see Figure 2). Maltose and isomaltose both contain a-glucoses in a(l—>4) linkages in the case of maltose, and in a(l—>6) linkages in the case of isomaltose. Maltose results from the hydrolysis of starch, and isomaltose from the hydrolysis of dextrans. Cellobiose is composed of /3-glucose oc-... 

Glucose/com syrups may be manufactured by either an acid or an acid-enzyme process. Acid-catalyzed hydrolysis was the traditional method of corn syrup production and is still the most common method for producing sweeteners up to about 42 DE. Since acid-catalyzed hydrolysis of sweeteners to 55 DE or above creates products of reversion, such as gentiobiose, isomaltose and trehalose, which give unacceptable flavors to the syrup, these syrups are usually made by acid-enzyme processes.18... 

During acid hydrolysis, 5 to 6 percent of glucose undergoes side reactions to produce reversion products. These are predominantly isomaltose and gentiobiose, and, in addition, other di- and trisaccharides. 

In this connection it may be mentioned that many ordinary yeasts ferment, generally very slowly, isomaltose and trisaccharides (limit dextrins) with one maltose and one isomaltose linkage. - Dried yeasts ferment starch and limit dextrins mth a fairly high velocity. This fermentation is probably not due to a hydrolysis of the saccharides to D-glucose or maltose, but to a phosphorolysis to the Cori ester (a-D-glucopyranose 1-phosphate). 

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