Glycogenin (GN), the protein moiety of mammalian and yeast proteoglycogen, initiates the polymerization of glucose by autoglucosylation from UDPG, a reaction that requires Mn++. The polymerization is continued by glycogen synthase (GS), which as GN utilize UDPG but no ADPG. Contrary to the mammalian and yeast enzymes the bacterial GS is specific for ADPG and it was claimed to be also responsible for initiation of the polymerization. We had described a 31 kDa protein linked to proteoglycogen in Escherichia coli, but no further characterization was done. Now we show that the rM of the glycogen-bound protein is 38-kDa. The protein is present in a proportion lower than the GN of liver proteoglycogen. Due to this, the search for a glycogenin-like activity was done without separation of amylase from the amylolyzed mixture, a procedure which might result in lost of the released protein. Thus, only the transglucosylation of DBM, whose reaction product is not substrate for amylase, was measured. When treatment with caotropic agent was omitted, the purified E. coli glycogen preparation contained GS activity which glucosylated DBM from ADPG but no from UDPG. The treatment with 3.6 M KI eliminated the GS activity. Free of GS, the amylolyzed glycogen glucosylated DBM from labeled sugar nucleotide. The reaction was Mn++-dependent and utilized UDPG but no ADPG. Our results are consistent with the presence of glycogenin-like protein bound glycogen in bacteria.
