The hexokinase of muscle and adipose tissue can accept fructose as a substrate, but K M is much higher for the furanose sugar than the usual pyranoses. Galactose is derived from breakdown of lactose in the digestive tract. This allows for activation to UDP-galactose . The new hydroxyl is randomly generated with either glucose or galactose configuration. This makes them suitable as glycosyl group donors .
Bacteria contain a variety of deoxy- and dideoxy sugars made by similar processes.