Enzymic determination of urinary free L-fucose

Conditions necessary for the precise measurement of free L-fucose in urine by an enzymic method using L-fucose dehydrogenase have been studied. The normal urinary levels of L-fucose were 16.4 /+- 9.1 micrograms/ml in children (22.2 /+- 6.5 micrograms/mg of creatinine) and 17.7 /+- 8.5 micrograms/ml in adults (16.6 /+- 5.7 micrograms/mg of creatinine). There was a close correlation between the concentration of free L-fucose and that of creatinine. A close correlation was also found between the concentration of free L-fucose and alpha-L-fucosidase activity. Thus, it was suggested that the free L-fucose in urine reflected the metabolism of L-fucose or L-fucose-containing glycoconjugates. In a preliminary screening test, several urine samples which showed high concentrations of free L-fucose, namely cases of "fucosuria" were found.