IDENTIFICATION OF N-ACETYLGLUCOSAMINE-ALPHA-1-PHOSPHATE TRANSFERASE-ACTIVITY IN DICTYOSTELIUM-DISCOIDEUM - AN ENZYME THAT INITIATES PHOSPHOGLYCOSYLATION

A lysosomal proteinase from Dictyostelium discoideum was previously shown to have GlcNAc alpha-1-P residues in phosphodiester linkage to serine. We have identified a GlcNAc-alpha-1-P transferase activity in membrane preparations using UDP[H-3]GlcNAc and a peptide acceptor with three tandem Ser-Gly repeats. We established an assay, proved the structure of the product, determined the Kms for donor and acceptor and showed that the glycopeptide binds a GlcNAc-alpha-1-P specific rabbit antibody. These findings provide the tools to search for mutants lacking GlcNAc-alpha-1-P transferase activity as a probe for the function of this modification we call phosphoglycosylation. (C) 1995 Academic Press, Inc.