Thesis (doctoral)--Lund University, 1997. / In the title, [beta] is represented by the Greek letter.

Thesis (doctoral)--Lund University, 1997. / In the title, [beta] is represented by the Greek letter.

It has recently been established that the activity of crystalline muscle phosphoglucomutase can be greatly stimulated by preincubation of the enzyme with a Mg++-imidazole complex. This observation has aroused interest in the physiological significance of such a system in the possible cellular control of phosphoglucomutase activity. The present study constitutes, in part, an investigation of the properties of phosphoglucomutase from brain tissue. A procedure for the purification of phosphoglucomutase from beef brain is described. The brain enzyme appears to be similar to that from skeletal muscle. Evidence is also presented which indicates that the "activation" produced by Mg++-imidazole is probably of no physiological importance in brain. This observation is consistent with the more recent reports that the phosphoglucomutase reaction is likely not involved in cellular regulatory mechanisms. It is well established that phosphofructokinase is intimately involved in the cellular regulation of glycolysis and the citric acid cycle. Control mechanisms of the phosphofructokinase reaction in mammalian tissues have been postulated on the basis of the complex kinetics of the enzyme. In yeast, however, two enzymatically interconvertible forms of the enzyme have been reported. Preliminary experiments in this study failed to demonstrate a phosphofructokinase system in brain similar to that found in yeast. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

In an earlier project completed in our laboratory a seasonal fluctuation in Phosphoglucomutase (PGM) phenotype frequencies was found, so that the winter bees were almost all heterozygotes and long lived than the summer bees among which homozygotes were significantly at high frequencies at Pgm locus. Same results were obtained in populations of three subspecies, A. m. meda, A. m. caucasica, and A. m. carnica from different climatic regions. In the current study environmental cues related with seasonal change in PGM phenotype frequency was examined along with the correlation between PGM heterozygosity and overwintering success. Cessation of food influx was found to be effective by itself as an environmental cue that causes a sudden and sharp increase in PGM heterozygosity. In addition to that, PGM heterozygosity of the colonies with greater overwintering success was found to be significantly higher than the ones with intermediate or low overwintering success. Benefiting from the previous studies and the results of current study, ethyl oleate was suggested as a chemical signal that functions in the regulation of PGM heterozygosity.

Phosphoglucomutase (PGM) is one of the central enzymes in energy metabolism at a branch point at the head of the metabolic pathway leading into glycogen metabolism, pentose shunt and the main glycolytic cycle, catalyzing the reversible interconversion of glucose-1-phosphate to glucose-6-phosphate. Whole year, month to month analysis of pattern of allozyme variation at Pgm and Hk loci in Apis mellifera L. from three provinces / Kirklareli, Artvin, and Hatay revealed that there is significant seasonal variation of allozyme frequencies at Pgm locus (P&lt / 0.001). The difference in genotype frequencies between summer and winter samples is apparent in Pgm, whereas at Hk locus, which is analyzed as a control there is seasonal variation in genotype frequencies. Biochemical measurements of the enzyme activities and glycogen content of different Pgm genotypes were performed to determine the effect of different Pgm genotypes on the physiological performance of the honeybees and it was observed that both enzyme activity and glycogen amount is higher in heterozygote individuals which are in high frequency during winter months (P&lt / 0.0001). Furthermore, PGM enzyme activity and glycogen content was found to be significantly correlated. These findings clearly demonstrate that biochemical differences between different Pgm genotypes have functional correlates that lead to significant variations in glycogen content of the honeybees and may have adaptive consequences.