Knowledge of glycosidase inhibitors may lead to more nutritious products.

A glycosidic bond is a covalent chemical bond that joins two simple sugars by means of an oxygen atom. We know that polysaccharides are carbohydrates containing thousands of glucose units joined by alpha or beta glycosidic bonds. We may be able to improve the nutrient content of food with new knowledge about enzymatic changes that occur in complex carbohydrates. Improving a product's nutrient content is the aim of European researchers working on the hydrolytic reactions of glycosidic bonds. They're learning how to possibly inhibit their function. The findings will improve the quality of a variety of products.

The enzymatic hydrolysis of complex carbohydrates containing alpha or beta glycosidic bonds has nutritional implications. These enzymes--glycosidases--include the amylases, pectinases and xylanases. They are present in many foods, but their microbial analogues are often produced and added in many food processing applications. They might find use, for instance, to improve the shelf life of bakery products; clarify beer; produce glucose, fructose or dextrins; hydrolyze lactose; or modify food pectins.

Amylase enzymes, which degrade alpha glysosidic bonds, are also produced in the digestive system to break down starch. However, many plant foods also contain endogenous inhibitors that reduce the activity of glycosidases, in particular proteins, peptides, complexing agents and phenolic compounds. The plant proteinaceous inhibitors are the focus of researchers who want to understand these inhibitory reactions and determine their biodiversity and expression in plants.

The results of their efforts will help optimize processing technologies by enabling us to use modified enzymes not influenced by the natural inhibitors. The scientists have already purified and produced several inhibitors of amylases, xylanases, polygalacturonases and pectin methylesterases. They have also isolated novel inhibitors and target enzymes, determined the x-ray structure of two novel xylanase inhibitors and identified the plant genes responsible for the enzymes and for producing inhibitors.

Additionally, they have studied the inhibition reaction and found some modified (mutant) xylanases produced from microorganisms which are independent of the plant inhibitors. Using these inhibitor-resistant xylanases in wheat, chicks fed the product utilized the feed more efficiently.

Baking trials using reconstituted flour are in progress, directly measuring the effect of xylanases and their inhibitors. Investigators also are studying the role of glycosidases and their inhibitors in plant resistance to invading microbia.

Further information. Nathalie Juge, Institute of Food Research, Norwich Research Park, Colney, Norwich, Norfolk NR4 7UA, England, U.K.; phone: [phone]; fax: [phone]; email: [e-mail].