[Alpha-mannosidase activity of different human biological fluids]

Two distinct alpha-mannosidases have been found in biological fluids by investigating the effect of pH on activity, the effect of Co2+ and Zn2+ and by determining the Michaelis constant. The two enzymes are designated as S, predominating in serum (optimum pH about 5.6) and U, predominating in urine (optimum pH about 4.2). In cerebro-spinal fluid, the amount of alpha-mannosidase S is almost the same as that of alpha-mannosidase U. Alpha-mannosidase S activity in sera is significantly higher in children than in adults.