1. ENZYMATIC GLYCOSYLATION
The transfer of a glycosyl moiety is one of the most important biochemical reactions in living beings. These processes are catalyzed by a wide diversity of glycosidic enzymes, which represent between 1% and 3% of the genes of an organism. Glycosidic bonds are present in a many bioactive glycosides and glycoconjugates. The two main groups of enzymes that act on carbohydrates are glycosidases (GHs, EC 3.2.1) and glycosyltransferases (GTs, EC 2.4). GHs catalyze the hydrolysis of di-, oligo- and polysaccharides, do not require cofactors, and present great availability. GTs transfer glycosyl residues from one activated substrate (sugar-nucleotides for the enzymes of the Leloir route; sugars-phosphate for the glycoside phosphorylases, GPs) to an acceptor. However, a series of GTs called transglycosidases (TGs, e.g. dextransucrases) use “non-activated” carbohydrates (sucrose, starch, etc.) as glycosyl donors. GHs and TGs catalyze both the formation of a glycosidic bond and its hydrolysis, allowing the use of hydrolytic enzymes in synthetic reactions. The following figure illustrates the different alternatives to glucosylate a model carbohydrate (galactose).
We are investigating different applications of carbohydrate-active enzymes, such as the preparation of prebiotic oligosaccharides for incorporation into functional foods or the synthesis of glycoderivatives of polyphenols. As a matter of fact, glycosylation dramatically changes the physico-chemical properties and bioavailability of many vitamins, hormones, flavonoids, antibiotics, etc.
2. ENZYMATIC ACYLATION OF POLYPHENOLS
The modification of natural antioxidants in order to increase their miscibility and/or stability towards the action of light and/or oxygen renders a series of “semisynthetic” antioxidants with great impact in the food and pharmaceutical industries.
The enzyme-catalysed synthesis of acyl derivatives of polyphenols offers some advantages, such as its high regioselectivity and the moderate reaction conditions. Lipases have been successfully used to catalyse the enzymatic acylation of different molecules employing saturated and unsaturated free fatty acids, alkyl or vinyl esters as acyl donors.
3. IMMOBILIZATION OF ENZYMES