Elucidation of the biochemical mechanism of glycogen phosphorylation in Escherichia coli

[摘要] ENGLISH ABSTRACT: Glycogen was isolated from E. coli and analysed for the amount of phosphatepresent within it. It was confirmed that a significant proportion of the glucose residueswere phosphorylated at the C6 position. This glycogen phosphate was found also inboth glgb- (glycogen branching enzyme) and glgp- (glycogen phosphorylase enzyme)mutants, demonstrating that a mechanism for phosphate incorporation that does notinvolve GlgP alone, and which is capable of incorporating phosphate into linearglucans could exist. The degree of phosphorylation depended on the amount ofphosphate present in the media, which less being incorporated in media wherephosphate was reduced. Screening for glycogen phosphorylating genes using a E.coli genomic library in a functional expression system identified the malP gene as apossible candidate for incorporation of the phosphate at the C6 position. There wasno difference, however, between the glycogen phosphate content of the mutant andwild type. Efforts were made to construct a malp-/glgp- double mutant, but these wereunsuccessful.In addition the influence of plants and human proteins on yeast glycogen metabolismwas also investigated. These proteins have been demonstrated to have an effect onstarch or glycogen in humans, plant and E. coli, but the data from this study indicatedthat this was not the case in yeast.

[发布机构] Stellenbosch University