Enzymes maltase

Wort. Wort is the Hquid drained off the mash tun containing maltose, a grain sugar derived from the conversion of starch during the mashing process by the action of the organic enzyme, maltase, found in badey malt. 

Many enzymes are extremely specific. For example, the enzyme maltase catalyzes the hydrolysis of maltose ... 

This reaction can be reversed either by using the enzyme maltase as a catalyst or by heating with acid. Two molecules of glucose are farmed when this happens. 

Prior to fermentation, the wort is then cooled to temperatures below 85°F (30°C), and the pH is adjusted to about 5. Yeast such as Saccharomyces cerevisiae, Saccharomyces carlsbergensis or Candida brassicae are added and fermentation proceeds for 2 to 3 days under batch processing conditions. Yeast produces the enzymes maltase, zymase, and invertase. Maltase converts maltose to glucose. Zymase converts glucose to ethanol. Invertase converts any sucrose present to fermentable sugar. The following equations illustrate the enzymatic conversion of starch to ethanol ... 

Maltose is hydrolyzed by the enzyme maltase (specific for a-glycosidic linkage) to two units of glucose, but for the hydrolysis of cellobiose the enzyme emulsin (specific for (3-glycosidic linkage) is necessary. While maltose is the building block of the polysaccharide starch, cellobiose is the building block of another polysaccharide, cellulose. 

Maltose ( malt sugar ), melting point of H2O 100°C. With the enzyme maltase yields glncose plus glucose. Specific rotatory power... 

With the enzymes maltase, or cellase, yields glucose plus glucose. 

With the enzyme maltase or with acids yields glucose. 

Amylase in the saliva and small intestine helps convert starch to maltose, and this in turn is converted into glucose in the small intestine with the enzyme maltase present. Glucose is either used for energy release or stored as glycogen for future use. 

A source of alcohol and alcoholic beverages. The starch of grains, potatoes, etc., is first hydrolyzed by natural sprouting, as in the preparation of barley malt, or by the addition of malt to it. The hydrolytic products, glucose and maltose, are then fermented by the addition of yeast, containing the enzymes, maltase, and zymase, and alcohol is thus produced. This has been fully discussed in the chapter on alcoholic fermentation, (p. 95). 

Maltose a-D-glucose + a-D-glucose a(1 -+4) Germinating cereal and malt Forms osazone with phenylhydrazme. Fermentable by enzyme maltase present in yeast. Hydrolysed to two molecules of D-glucose. Undergoes mutarotation. 

The Chemical Changes during Fermentation—Before the maltose present in the wort can be fermented it must be converted into a corresponding amoimt of dextrose which is effected by the enzyme maltase secreted by yeast. In like manner cane sugar must first be converted into equal molecules of dextrose and levulose by the enzyme invertase, which is also secreted by yeast. It is only the hexoses which are directly fermentable. The conversion of dextrose into alcohol and carbon dioxide according to the equation CgHioOg =2C H6O - -2CO2is only the main portion of tlie... 

This is brought about by the enzyme maltase contained in ordinary yeast. 

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. 

Maltose is a disaccharide of glucose units joined oi-1,4. It differs from cellobiose, which is also a glucose disaccharide with units joined / -1,4. The enzyme, maltase, catalyzes hydrolysis of maltose to two molecules of D-glucose. 

The digestion and metabolism of carbohydrates is a complex biochemical process. It starts in the mouth, where the enzyme amylase in the saliva begins the hydrolysis of starch to maltose and temporarily stops in the stomach, where hydrochloric acid deactivates the enzyme. Digestion continues in the intestines, where the hydrochloric acid is neutralized and pancreatic enzymes complete the hydrolysis to maltose. The enzyme maltase then catalyzes the digestion of maltose to glucose ... 

Another remarkable property of enzymes is their specificity of reaction that is, a certain enzyme will catalyze the reaction of a specific type of substance. For example, the enzyme maltase catalyzes the reaction of maltose and water to form glucose. Mal-tase has no effect on the other two common disaccharides sucrose and lactose. Each of these sugars requires a specific enzyme— sucrase to hydrolyze sucrose, lactase to hydrolyze lactose. (See the hydrolysis equations in Section 20.2.)... 

Johnson knew that the total and specific activities of maltase, sucrase, lactase, trehalase, palatinase, and peroxidase decrease in the intestines of parenterally fed rats. To determine the effect of pentagastrin upon the enzymes, Johnson measured the specific activities of the two brush border enzymes, maltase and sucrase, and of peroxidase, an enzyme confined to the lamina propria. He found that pentagastrin addition to intravenous feeding prevented the decline in the brush border enzymes but not in the lamina propria enzyme. This, as well as the effect of pentagastrin on oxyntic mucosal weight, Johnson concluded, is the result of the trophic action of gastrin, not of its ability to stimulate secretion, for histamine in all instances failed to have the effect of pentagastrin. " ... 

PROBLEM 22.51 Maltose is a disaccharide that differs very httle from ceUobiose. It has the same properties as cellobiose described in Problem 22.24, but is not cleaved by lactase (it is cleaved by another enzyme, maltase). Provide a three-dimensional structure for maltose. Hint-. How else can the two sugars be hnked ... 

In this arrangement, one glncose retains its unprotected hemiacetal unit with its distinctive chemistry. For example, maltose is a reducing sugar it forms osazones, and it nndergoes mntarotation. Maltose is hydrolyzed to two molecules of glucose by aqueous add or by the enzyme maltase. It is abont one-third as sweet as sucrose. 

Maltose consists of two molecules of glucose that are linked by an 0C-(1,4 ) glycosidic bond. Maltose results from the enzymatic hydrolysis of amylose, a homopolysaccharide (Section 26.9), by the enzyme amylase. Maltose is converted to two molecules of glucose by the enzyme maltase, which hydrolyzes the glycosidic bond. Commercial maltose is produced from starch that has been treated with barley malt. Figure 26.8 shows both a bond-line structure and a molecular model of maltose. 

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