Identification of an Endogenous Inhibitor of the UDP-N-Acetylgalactosamine: GM3, N-Acetylgalactosaminyl Transferase as Apolipoprotein A1 |
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Authors: | Conde Cecilia B. Grabois Viviana R. Deza Susana N. Caputto Beatriz L. |
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Affiliation: | (1) Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET) - Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, CC 61-5016 Córdoba, Argentina |
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Abstract: | A previously described inhibitor of the UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyltransferase (GalNAc-T) (Quiroga et al., 1,2), was purified from chicken blood serum by a new procedure. When subjected to SDS-PAGE, two major polypeptides of 27 and 70 kDa were observed. When tested in vitro, only the 27 kDa polypeptide inhibited the GalNAc-T. When added to chick cerebral embryonic neurons in culture, both polypeptides inhibited neuritogenesis. Both the 27 kDa and the 70 kDa fractions were present in the cells at 3 h following their addition to the cultures; both polypeptides had aneuritogenic activity and both inhibited the incorporation of [3H]-galactose into the cell gangliosides modifying their labeling pattern to a similar extent. Sequencing of the amino terminal end of the polypeptides showed that 18 and 9 amino acids from, respectively, the 27 and the 70 kDa polypeptides, were 100% homologues with the corresponding region of chick apolipoprotein A1 (apo A1). After addition to cells in culture, no interconversion between the two polypeptides was detected after up to 20 h in culture. A monoclonal antibody that recognizes only the 70 kDa polypeptide, blocks its aneuritogenic effect without modifying that of the 27 kDa fraction. It is concluded that the endogenous inhibitor of GalNAc-T is apo A1. |
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Keywords: | GalNAc-T inhibitor apolipoprotein A1 ganglioside biosynthesis apolipoprotein A1 monoclonal antibody |
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