------O------- | | CH_{2}OH·CHOH·CH·CHOH·CHOH·CH | O | CH_{2}OH·CHOH·CH·CHOH·CHOH·CH | | ------O------- Trehalose may be hydrolyzed into glucose by dilute acids and by the enzyme "trehalase," which is contained in many yeasts and in several species of fungi. It is strongly dextrorotatory (specific rotatory power, +199°). It is not fermentable by yeast. Trehalose appears to replace sucrose in those plants which contain no chlorophyll and do not elaborate starch. The quantity of trehalose in such plants reaches a maximum just before spore formation begins. Since it is manufactured in the absence of chlorophyll, its formation must be accomplished by some other means than photosynthesis, yet it is composed wholly of glucose--a natural photosynthetic product. =Maltose= rarely occurs as such in plants, although its presence in the cell-sap of leaves has sometimes been reported. It is produced in large quantities by the hydrolysis of starch during the germination of barley and other grains. This hydrolysis is brought about by the enzyme "diastase," which is present in the sprouting grain. Maltose is easily soluble in water, and crystallizes in masses of slender needles. It is a reducing sugar; readily forms a characteristic osazone; is strongly dextrorotatory (specific rotatory power +137°); and is readily fermented by ordinary brewer's yeast, which contains both "maltase" (the enzyme which hydrolyzes maltose to glucose) and "zymase" (the alcohol-producing enzyme). When hydrolyzed, either by dilute acids or by maltase, one molecule of maltose yields two molecules of glucose. Its component hexoses are, therefore, the same as those of trehalose, a non-reducing sugar, this difference in properties being due to the difference in the point of linkage between the two glucose molecules, that for maltose being such as to leave one of the aldehyde groups potentially active, as shown in the following formula, -------O------ | | CH_{2}OH·CHOH·CH·CHOH·CHOH·CH | O | CHOH·CHOH·CHOH·CH·CHOH·CH_{2} | | ----------O-----