The oligosaccharide portion of glycoproteins is known to modulate protein structure, function, and turnover. Our laboratory is interested in the metabolism of L-fucose, a normal constituent of eukaryotic glycoproteins. L-Fucose is unique in that it is the only levorotatory sugar utilized in mammalian systems. There is considerable interest in understanding the controls which determine the level of L-fucose attached to proteins, in order to generate stable and active glycoforms of protein for the treatment of disease. As part of a program to determine the controls on protein L-fucosylation, we have systematically determined the tissue distribution of the enzymes L-fucokinase and α-L-fucosidase in species across the vertebrate animal kingdom. In general, the level of α-L-fucosidase is higher than L-fucokinase level. The tissue with highest enzyme activity cannot be generalized, regardless of which enzyme is of interest. Furthermore, there is not a correlation between synthetic and catabolic enzyme activity within a tissue. L-Fucokinase can be detected in all tissues examined. Interestingly, we have also detected β-D-fucosidase activity, present in extraordinary levels in the liver and small intestine of snake. Whether this is due to a specific enzyme or whether it represents a broad specificity of the α-L-fucosidase is currently being investigated.