The branched tetrasaccharide, O-beta-D-glucopyranosyl-(1 --> 2)-O-[beta-D-xylopyranosyl-(1 --> 3)]-O-beta-D-glucopyranosyl-(1 --> 4)-D-galactose (lycotetraose) is a key constituent of many biologically interesting natural products. Described herein is a convenient enzymatic preparation of lycotetraose from the readily available Solanum glycoalkaloid alpha-tomatine. The preparation makes use of the recombinant endo-glycosidase, tomatinase, from the plant pathogen Fusarium oxysporum f. sp. lycopersici. (C) 2004 Elsevier Ltd. All rights reserved.