Comparative analysis of the glg operons of Pectobacterium chrysanthemi PY35 and other prokaryotes

A chromosomal region of Pectobacterium chrysanthemi PY35 that contains of genes for glycogen synthesis was isolated from a cosmid library. The operon consists of glycogen branching enzyme (glgB), glycogen debranching enzyme (glgX), ADP-glucose pyrophosphorylase (glgC), glycogen synthase (glgA), and glycogen phosphorylase (glgP) genes. Gene organization is similar to that of Escherichia coli. The purified ADP-glucose pyrophosphorylase (GlgC) was activated by fructose 1,6-bisphosphate and inhibited by AMP. The constructed glgX::Omega mutant failed to integrate into the chromosome of P. chrysanthemi by marker exchange. Phylogenetic analysis based on the 16S rDNA and the amino acid sequence of Glg enzymes showed correlation with other bacteria. gamma-Proteobacteria have the glgX gene instead of the bacilli glgD gene in the glg operon. The possible evolutionary implications of the results among the prokaryotes are discussed.