Characteristics of human intestinal acid sialidase.

With methylumbelliferyl-N-acetyl-neuraminic acid (MU-NANA) as substrate, acid sialidase was determined in intestinal biopsies of children. The enzyme has an acid pH optimum, a Km value of 4 mmol/l and a pronounced thermal lability which can be partially prevented by the addition of albumin. N-acetyl-neuraminic acid (NANA) and derivatives as well as other glycoprotein and oligosaccharide sialidase substrates inhibit sialidase whereas gangliosides have no effect. This could be an indication that intestinal MU-NANA sialidase is different from ganglioside sialidase as has been reported for many other tissues.