Characteristics of maltase activity in amniotic fluid.

The nature and origin of maltase activity present in amniotic fluid, and used as a marker enzyme in the prenatal monitoring of cystic fibrosis, has been studied. Using monoclonal antibodies against human intestinal disaccharidases and via heat inactivation experiments it is shown that the maltase activity found in amniotic fluids from pregnancies of 16-24 wk of gestational age originates completely from sucrase-isomaltase; no maltase-glucoamylase could be detected. With various monospecific antibodies the possible contribution of non-intestinal brush border enzymes to the total maltase pool could be excluded: neither renal nor lysosomal maltase appeared to be present.