Biosynthesis of bacterial glycogen: purification and structural and immunological properties of Rhodopseudomonas sphaeroides ADPglucose synthetase.

ADPglucose synthetase from the photosynthetic bacterium Rhodopseudomonas sphaeroides was purified to greater than 95% purity. The molecular weight of the R. sphaeroides enzyme, as determined by sucrose density gradient ultracentrifugation, was approximately 204,000. The subunit molecular weight of the enzyme based on sodium dodecyl sulfate-gel electrophoresis was 46,000. Although the amino acid composition of the enzyme was similar to that found for the enzymes from Escherichia coli, Salmonella typhimurium, and Rhodospirillum tenue, no apparent homology has been observed between the N-terminal or C-terminal amino acid sequences. Antisera prepared against the ADPglucose synthetase could inhibit the activities of the enzyme from other photosynthetic bacteria. Therefore, some sequence homology may exist within the internal portion of their peptide chain.