Browsing by Author "Nepembe, Mehafo, Ndafapawa"

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    Elucidation of the biochemical mechanism of glycogen phosphorylation in Escherichia coli
    (Stellenbosch : University of Stellenbosch, 2009-12) Nepembe, Mehafo, Ndafapawa; Lloyd, James Richard; Kossmann, J. M.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics. Institute for Plant Biotechnology.
    ENGLISH ABSTRACT: Glycogen was isolated from E. coli and analysed for the amount of phosphate present within it. It was confirmed that a significant proportion of the glucose residues were phosphorylated at the C6 position. This glycogen phosphate was found also in both glgb- (glycogen branching enzyme) and glgp- (glycogen phosphorylase enzyme) mutants, demonstrating that a mechanism for phosphate incorporation that does not involve GlgP alone, and which is capable of incorporating phosphate into linear glucans could exist. The degree of phosphorylation depended on the amount of phosphate present in the media, which less being incorporated in media where phosphate was reduced. Screening for glycogen phosphorylating genes using a E. coli genomic library in a functional expression system identified the malP gene as a possible candidate for incorporation of the phosphate at the C6 position. There was no difference, however, between the glycogen phosphate content of the mutant and wild type. Efforts were made to construct a malp-/glgp- double mutant, but these were unsuccessful. In addition the influence of plants and human proteins on yeast glycogen metabolism was also investigated. These proteins have been demonstrated to have an effect on starch or glycogen in humans, plant and E. coli, but the data from this study indicated that this was not the case in yeast.