Structural analysis of human adult and fetal alkaline phosphatases by cyanogen bromide peptide mapping.

Publisher Website
Google Scholar
Abstract
The adult and fetal forms of human intestinal alkaline phosphatase (ALPase; orthophosphoric-monoester phosphohydrolase, EC 3.1.3.1) are indistinguishable by a variety of analytical procedures. They differ electrophoretically and can be differentiated by binding studies with monoclonal antibodies. These 2 enzymes along with placental and liver ALPases are compared by the technique of CNBr peptide mapping, and the role of carbohydrate in generating these patterns is investigated. NaDodSO4/PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] of CNBr digests of radiolabeled ALPases from fetal and adult intestine shows that these 2 isozymes share 5 of 7 common-sized CNBr fragments. Placental ALPase shares only one common-sized fragment with either intestinal enzyme. Liver ALPase has no CNBr fragments in common with any of the others. Fetal intestinal ALPase is not a heterodimer of 1 subunit each of intestinal ALPase and placental ALPase as has been postulated. CNBr digests of neuraminidase-treated enzymes reveal a change of mobility of only 1 CNBr band in each of fetal intestinal, placental, and liver ALPases, indicating the presence of sialic acid residues in these fragments. Periodic acid/Schiff reagent staining (specific for carbohydrate) of CNBr digests of fetal and adult intestinal ALPases reacts with only 1 band in each enzyme, which is the same band from the fetal enzyme shown to contain sialic acid. Fetal and adult intestinal ALPases each contain at least 1 CNBr fragment of unique size that is apparently nonglycosylated. [Genetic implications are discussed].