Publisher Summary This chapter discusses the results of the studies that permit some generalizations on the catalytic mechanism of glycoside hydrolases from widely differing sources and with different sugar and aglycon specificities and that have become available over the past 15 years. The strong inhibition of glycosidases by aldonolactones was first mentioned in 1940 by Japanese workers who studied β- D -glucosidases from Aspergillus (Taka-diastase) and almonds. Even though both of these groups of compounds are derived from normal substrates by only a minor modification of the glycon moiety, they are discussed together with pseudosubstrates because their reactions with glycosidases show, in many cases, unusual kinetic features. The information relevant to the mechanism of an enzyme-catalyzed reaction can, in general, only be obtained from irreversible inhibitors that react specifically at the active site, and thereby inactivate the enzyme. In many cases, inhibition studies were not carried out to obtain information on the reaction mechanism, but for other purposes. Thus, only inhibitors were tested that were considered suitable for the particular project, for example, studies on the biological function of the enzyme where glycosylamines and aldonolactones are unsuitable.

Glycoside Hydrolases: Mechanistic Information from Studies with Reversible and Irreversible Inhibitors

Medicinal plants in the Mediterranean area: Synthesis of the results of the project Rubia

The present paper reviews the occurrence of glycosidically bound aroma compounds in the plant kingdom and discusses different hypotheses concerning their role in plants. Emphasis is on biotechnological methods for flavor release and flavor enhancement through enzymatic hydrolysis of glycoconjugated aroma substances.

Glycoconjugated aroma compounds: occurrence, role and biotechnological transformation.

Potent competitive inhibition of α-galactosidase and α-glucosidase activity by 1,4-dideoxy-1,4-iminopentitols: syntheses of 1,4-dideoxy-1,4-imino-d-lyxitol and of both enantiomers of 1,4-dideoxy-1,4-iminoarabinitol

Five years ago, in 1986, only a limited number of glycosidically bound volatiles were known and little could be reported on the distribution of those compounds in the plant kingdom. Since then an explosion of research activities in this field has led to the publication of many interesting results concerning structurally diverse terpenoid and non-terpenoid glycosides, their occurrence, and their role in different plant species. Up to now, about 200 different aglycone structures have been found in about 150 species belonging to 35 different families including ferns, gymnosperms, dicotyledons, and monocotyledons.



All the diverse results concerning the role of these compounds in the plants should not lead us into ascribing to them an exclusive role, such as being involved in essential oil metabolism, as early workers have postulated. Although considering new electron microscopical observations of a transformation of carbohydrate-rich substances into lipophilic droplets at the tonoplast of Mentha × piperita secretory cells, the range of possible roles should not be underestimated. New experimental work should not only provide new analytical data but should also attempt to throw more light on the role of the glycosides.

C. Zdero

Papers

Sesquiterpene lactones from Lactuca sativa

Glaucolide-like sesquiterpene lactones from Artemisia judaica

Sesquiterpene xylosides from Iphiona scabra

A heliangolide from Tanacetum santolinoides