Invertase Yeast emulsin

In 1896, Fischer developed the phenylhydrazine test" for the detection of hydrolytic scission of disaccharides, especially by enzymes this depends on the fact that the phenylosazones of disaccharides are soluble in hot water, whereas those of the monosaccharides are not. Lactose is hydrolyzed by emulsin (1894) and by lactase it is not fermentable by yeast, and is unaffected by invertase (1894). An extract of the small intestine of horses and cattle, especially from young animals, hydrolyzes lactose (1896). The action of enzymes on lactose allowed it to be classified, along with cellobiose and maltose, with the normal (and not the y-type of) methyl glucoside (1914). In the discussion of maltose, the relationship of lactose to the /9-series will be mentioned later. 

In further work, Strepkov obtained99 labiose in crystalline form, of m.p. 126-8°, [c ]d + 136.7° (in water, air-dry basis). Labiose is completely hydrolyzed by invertase at 47-8° in 20 hours, and by 1% hydrochloric acid at 68-70° in 10 to 12 minutes, to give one molecular proportion of D-galactose and two molecular proportions of D-fructose. Labiose is not hydrolyzed by almond emulsin, and it is fermented but little by pressed yeast. Strepkov concluded that labiose is related to the alpha series ( ) and that, probably, the D-galactose unit is in the center of the molecule. 

Changes of Ring Structure and Configuration. When the structure of a hydrolyzable pyranoside is changed to that of a furanoside, the latter is unaffected by the enzyme. Thus, the a- and jS-D-glucofuranosides are unaffected 36) by almond emulsin as well as by yeast a-glucosidase (yeast maltase). Similarly, yeast invertase catalyzes the cleavage of sucrose and other jS-fructofuranosides, but not that of the known fructopyranosides 37). 

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