The Digestion and Inactivation of Maltase by Trypsin and the Specificity of Maltases

Abstract

In 1925 Leibowitz (1) proposed the theory that there are two kinds of maltases,--one kind present in yeast, having the power of hydrolyzing maltose and a-methylglucoside and another found in moulds (2--4) with only maltose-splitting power. Thus he would differentiate between glucosidomaltase and glucomaltase. But Weidenhagen (5) has taken quite a different view. He thinks that sucrose may be hydrolyzed by a-glucosidase and by a/~-h-fructosidase, and maltose only by a-glucosidase. This he explains by his steric configurative theory, according to which one and the same enzyme, a-glucosidase, must be able to hydrolyze sucrose, maltose, and a-glucosides since each has an a-glucosido rest bound to a glycone or an aglycone. In other words this means that the classical nomenclature of maltase, sucrase, etc., would have to be dropped, since such separate enzymes would not exist. Recently we (6) have shown the maltase of the mammary gland to be unmistakably a glucomaltase, hydrolyzing maltose but not sucrose or a-methylglucoside, thus corroborating the theory of Leibowitz. Doubt has been cast upon Weidenhagen's work (7) from another angle by Karstroem (8), Myrbaeck (9), and Virtanen (10) who found that the enzyme of a certain strain of B. colt can hydrolyze maltose but not cane sugar. Experiments on moulds by Pringsheim, Borchard, and Loew (11) speak also against the theory of Weidenhagen.Since, in enzyme chemistry, the question whether there are distinct maltases and sucrases is of considerable importance, we have undertaken to procure additional data by studying the maltase of saliva and the maltase produced by Escherichia colt. For the determination of enzyme activity we have used an improved technic. We have utilized our new method (12) which permits of the determination of minute 767

The Chemical Nature of Enymes.

“…It has also been shown by Tauber and Kleiner (82) that maltase is readily digested by trypsin. Tauber (78) found emulsin to be indigestible by pepsin, trypsin, and pancreatin during several weeks incubation at 40°C.…”

The metabolism of the oral flora. 2. The oxidation of some sugars by mixed human saliva

“…We found that sucrose was, in all except one of the subjects, metabolized at least as rapidly as glucose by the saliva. There is some disagreement in the literature concerning the existence of invertase in saliva (Bourquelot, 1910;Lisbonne, 1910;Tauber & Kleiner, 1933;Wohrinz, 1938;Volker, 1950). The fact remains, however, that unfiltered whole saliva can metabolize the disaccharides sucrose and maltose no less readily than glucose.…”