Maltose occurrence

Several applications of these couplings to the conformational analysis of various mono- and oligosaccharides have also been described.138 140 143 149 150 These applications incorporate both theoretical and experimental approaches toward determination of the conformation of saccharides in solution, a question still controversial because of the time-averaged character of the NMR data obtained (NOE and couplings) and the occurrence of conformational equilibria.3 Variations of Vc H values for maltose according to the solvent used have been observed,46 and... 

The hydrolytic action of beta-amylase results in the formation of maltose in the /8-anomeric form. In contrast to the widespread distribution of the a-amylolytic enzymes with their difiPering properties, the occurrence of beta-amylase appears to be restricted entirely to the higher plants and, furthermore, enzymes from different sources behave similarly. befa-Amylase appears to be a simple enzyme, and there is no evidence for the necessity of coenzymes, metals, or nonprotein active-groups. 

The /3-amylase liberates the maltose in the /S-configuration. This is no proof for the occurrence of /3-D-glucosidic linkages in starch. On the other hand, it is not known why the /3-amylase, in contrast to the a-amylases, causes an inversion of the configuration. 

Hexabioses.—Maltose.—Almost the sole occurrence of this sugar is in the product of the hydrolysis of starch either by the action of enzymes or by acid hydrolysis. It is not isolated but is fermented in the solution in which it is prepared. The enzyme, maltase, is usually elaborated by the same yeasts as carry on the fermentation. This enzyme converts the maltose into two equivalents of dextrose which are then directly fermentable. When isolated, maltose forms hard white crystalline masses, very similar to grape sugar. It is determinable by the facts that its solutions have some reducing power (about two-thirds that of glucose), and that its solutions are strongly dextro-rotary. 

Starch.- —While many fermented liquors obtain sugar for conversion into alcohol from sources indicated above by far the largest single source of sugar, especially for distilled liquors, is the poly-saccharide, starch. Its importance arises from the fact that by suitable treatment almost 100% conversion of starch into fermentable sugars, dextrose, maltose, etc. can be obtained. Hence the general nature, occurrence and physical and chemical properties of starch are of major interest in the fermented liquor industry. 

Occurrence. Maltose occasionally has been recorded as present in intact... 

The immediate production of maltose by jS-amylase has led to its being called maltogenic amylase. In all cases iS-amylase produces only jS-maltose and none of the a-anomers. The mechanism of the inversion of the ano-meric carbon atom during cleavage by the enzyme is unknown. The occurrences of i -amylase activity is restricted to higher plants. 

In the phloem sap of Betula pendula at 0°C, sugars found (in order of concentration) were D-fructose > sucrose > stachyose > D-glucose > maltose > raffinose, while in the xylem sap the order was D-fructose > D-glucose > sucrose > > stachyose (149). The ubiquitous occurrence of D-glucose and D-fruc-tose is exemplified by its presence in sap (149, 150), bark (179), roots (109), and trunkwood (93). 

The observed single inversion in the phosphorolysis of maltose may be explained on the basis of a three-component system in which the phosphate transfer occurs between the substrates rather than between the enzyme and each substrate separately. The occurrence of the inversion would indicate that the carbon oxygen bond of the phosphate ester is broken, as has been shown in the case of sucrose phosphorylase. ... 

When starch is heated in water to 60-80°C the starch grains swell and yield two components. One component (amylose) is water-soluble, is entirely degraded to maltose by the ]S-amylase and its molecules consist of unbranched spiral chains of glucose units (300-1000 units) linked by 1 4 a-linkages. The second component (amylopectin) is not soluble, yields both maltose and dextrin on treatment with )8-amylase and has a branched chain structure due to the occurrence not only of 1 4 but also of 1-6 linkages between the glucose units (Fig. 5.11). 

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