Maltase, preparation

The maltase reaction can be reversed. " C-labeled glucose incubated in the presence of a maltase preparation obtained from the intestinal mucosa can be incorporated into maltose. 

It is important to note that no evidence of maltase activity was found in the amylase preparations even when the highest concentrations used in these comparisons were allowed to react for twenty-four hours with one per cent maltose under the conditions for the hydrolysis of starch. Similarly, no evidence was obtained for the presence of any other contaminating or extraneous carbohydrases in the amylase preparations. Partial inactivation of the amylase under a number of different conditions failed to give any evidence of selective inactivation such as might be expected if more than one enzyme were present. The substrates used for measuring the activity of the partially inactivated amylase were starch and starch hydrolyzates that had already been extensively (58) J. Blom, Agnete Bak and B. Braae, Z. physiol. Chem., 250, 104 (1937). 

Arrowroot starch, approximately 2% pH 5.3 maltase-free amylase prepared according to Ohlsson23 from malted barley extract and purified by precipitation with alcohol. 

Although dilute aqueous acid hydrolyzed the methyl and benzyl a-D-fructofuranosides approximately 8 and 16 times as rapidly as sucrose, their method of preparation showed them to be unaffected by any of the enzymes active in a fermenting yeast suspension. Purified yeast invertase, proven free of a-D-glucosidases (maltases), could therefore contain no enzyme capable of hydrolyzing the above two a-D-fructo-furanosides, but did contain constituents that readily cleaved the beta isomers and also sucrose. The latter is accordingly a /S-D-fructofuranos-ide. When the evidence is put in this way, the present uncertainties as to whether purified invertase preparations include one or a number of /3-D-fructofuranosidases, and whether or not sucrose, methyl and... 

Reaction of benzyl a-D-glucopyranosyl cyclic sulfate 44 or benzyl a-D-galactopyranosyl cyclic sulfate 45 with 1,4-anhydro-2,3,5-tri-0-benzyl-4-thio-D-arabinol 46, followed by debenzylation and reduction, gave novel sulfonium sulfate derivatives 47a and 47b, respectively, which were used to prepare homologs of salacinol 48, a natural human maltase glucoamylase inhibitor, as lead candidates for the treatment of type 2 diabetes (Scheme 3) <2006JOC1111>. 

It is not easy to show that a preparation of malt a-amylase is enzy-mically homogeneous and free from /3-amylase and maltase. As will be shown later, the enzyme liberates D-glucose as a primary product from starch. Thus the appearance of D-glucose is not evidence of the presence of maltase. But the absence of this enzyme is most easily demonstrated... 

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). 

In these various ways, the anomeric forms of methyl, ethyl and benzyl thioglucosides and n-propyl -thioglucoside were all prepared in pure crystalline form. They are typical glucosides, non-reducing, stable toward alkalies, hydrolyzed by acid, but not by emulsin, myrosin or yeast maltase. 

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. 

Commercial, bovine-serum albumin preparations contain alpha-amylase or maltase activity, or both. 

The method gave results in good agreement witii those afforded by other methods, but it has since been criticized, the bases for the criticism being the possible interference by the reduced glutathione used to stabilize the befa-amylase and the possible effect of maltase impurity in the latter enzyme. However, the availability of preparations of maltase-free beto-amylase (see Section IV,l,b p. 288) showing no instability has rendered these criticisms no longer viable. 

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