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The action of enzymes of almond emulsin on the phenyl glycosides of a number of sugars which are not naturally occurring has been investigated. The sugars used were synthetic heptoses (d-a-mannoheptose and d-a-glucoheptose) and d-talose. The results obtained indicate that almond emulsin docs not hydrolyze all glycosides but instead only the glycosides of naturally occurring sugars or of sugars which may be considered to be derived from these sugars by a simple substitution outside of the pyranose ring. In the ordinary glucoside the two parts are connected through an oxygen atom. It has now been found that the substitution of this oxygen by sulfur atom reduces the hydrolytic action to such an extent that it cannot be readily measured. An explanation for this effect is given. CONTENTS Pn':l I. "Sugar specificity" of the glycosidases  ___ 197 II. P-Thiophenyl d-glucoside  199 III. Experimental details ___ __  200 1. Preparation of substrate solutions  __ _ 200 2. Enzyme solution  201 3. Hydrolysis measurements  201 (a) Phenyl glycosides __  201 (b) P-Thiophenyl d-glucoside  202 4. Calculation of results __   202 I. "SUGAR SPECIFICITY" OF THE GL YCOSIDASES 1 An explanation of the specificity to be expected of the glycoside hydrolyzing enzymes has been given previously.2 The fundamental concept involved is that each of the alpha and beta isomers and d and l forms of the eight basic hexose types (glucosides, galactosides, mannosides, talosides, gulosides, idosides, altrosides, and allosides) requires a special enzyme. However, glycosides which have the same ring conformation and which may be considered as being derived from one of the basic hexose types by a substitution in the aglucon group or for the CH20H group will ordinarily be hydrolyzed by the same enzyme. Only those enzymes are to be expected in natural products which are capable of hydrolyzing glycosides of which the basic ring type is the same as that of a naturally occurring glycoside. 1 This paper was read before the Division of Sugar Chemistry and Technology of the American Chemical Society at Detroit, Mich., September 1940. I W. W. Pigman, J. Am. Chern. Soc. 62, 1371 (1940) .

Action of almond emulsin on the phenyl glycosides of synthetic sugars and on beta-thiophenyl d-glucoside