Maltose and isomaltose

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). 

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. 

Figure 2. Synthesis of maltose and isomaltose from ft-o-glucopyranose by glucoamylase, compared with the known hydrolytic reactions. The configurational inversion observed in the condensations indicates that the D-glucopyranosyl part of fi-D-glucopyranose is interchanged with hydrogen at the C, or C6 site of a second D-glucose molecule (78).

It should, however, be noted that maltose and isomaltose also have dextro-rota-tions greater than that of glucose. 

I. D. Fleming and H. F. Pleger, The determination of glucose in the presence of maltose and isomaltose by a stable, specific enzymic reagent, Analyst, 88 (1963) 967-970. 

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-... 

Meiler et al applied the model-free approach to the dynamic interpretation of residual dipolar couplings in globular proteins. Ishima et aO compared the methyl rotation axis order parameters derived from the model-free analyses of the and longitudinal and transverse relaxation rates measured in the same protein sample. Best et al reported the results of molecular dynamics simulations compared with NMR relaxation experiments for maltose and isomaltose. Using the model-free formalism they could estimate reliable order parameters. Baber et used an extended model-... 

D. Maltase and isomaltase convert maltose and isomaltose into glncose. 

By analogy with maltose and isomaltose, altemansucrase from Leuconostoc mesenteroides NRRL B-21297 was found to synthesize from gentiobiose as acceptor a series of gentiooligosaccharides that could be used as potential prebiotics, without the bitterness imparted by gentiobiose [86]. Altemansucrase also catalyzes... 

The earlier conclusion of Meyer that D-glucose, maltose, and isomaltose are the products of the a-amylolysis of amylopectin is now seen to be incorrect. 

The human organism hydrolyzes sucrose, lactose and oligosaccharides of the maltose and isomaltose type. The enzyme lactase, which is responsible for lactose hydrolysis, is lacking in some adults. Glucose and galactose are actively transported, while all other monosaccharides are transported only by diffusion. Sugar phospho-... 

Both maltose and isomaltose arise from the digestion of starch. 

Disaccharide A sugar consisting of two monosaccharides linked by a glycoside bond. The common dietary disaccharides are sucrose (cane or beet sugar), lactose, maltose and isomaltose. 

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