Isolation and characterization of two particle-bound oligoaminopeptidases from human meconium that are different from oligoaminopeptidase of adult small intestine.

Two oligoaminopeptidases (substrate L-leucyl-beta-naphthylamide) have been separated by ion exchange chromatography after Triton solubilization of meconial particles. The quantitatively major form (oligoaminopeptidase II) has been purified to apparent homogeneity. The two meconial oligoaminopeptidases differ from each other in their polyacrylamide gel electrophoretic mobility and isoelectric points. Both meconial enzymes differ from the adult enzyme by having more acidic isoelectric points and different affinities to Helix pomatia lectin-Sepharose columns. Oligoaminopeptidase II has a faster anodal electrophoretic mobility than the adult enzyme but a similar apparent molecular weight and subunit structure. Extensive neuraminidase digestion of meconial oligoaminopeptidase II does not modify the gel electrophoretic mobility of the enzyme. The charge difference between adult and meconial human brush border oligoaminopeptidases is therefore probably due, at least in part, to differences in the carbohydrate composition of these glycoproteins, and differences in the number of terminal or exposed sialic acid residues do not explain the observed charge differences.