Studies on isoamyalse formation in biological fluids.

Storage of human serum, saliva and duodenal secretion transformed amylase fractions on cellulose acetate membranes into more anionic forms. Incubation with lectins, proteases, glucosidases, neuraminidase and some effectors did not modify this conversion, which was promoted by rising temperature and pH values. Increasing concentrations of ammonium ions delayed the transformation of amylolytic fractions, thus indicating nonenzymatic deamidation as the reason for isoamylase development. A change of molecular weight could be excluded.