The Activity of Parafusin Is Distinct from That of Phosphoglucomutase in the Unicellular Eukaryote Paramecium

In this paper we identified the presence of a Paramecium phosphoglucomutase enzymatic activity which is clearly distinct from that of parafusin - the exocytosis-related phosphoglycoprotein. Since the recently cloned parafusin showed homology to rabbit muscle phosphoglucomutase, we have designed a specific peptide parafusin antibody - generated to a region not present in any known sequenced phosphoglucomutases - to distinguish parafusin from the Paramecium phosphoglucomutase. Separation of these two proteins was obtained using liquid chromatography, enzymatic activity assay and immunoblotting analysis with the specific parafusin peptide antibody. Parafusin fractions incorporated [β³⁵S]UDP-Glc but not [³⁵S]Glc-1-P, whereas Paramecium phosphoglucomutase fractions incorporated [³⁵S]Glc-1-P but not [β³⁵S]UDP-Glc. This indicates that these two proteins are separate entities exhibiting different properties and most likely distinct functions in the cell.