The phosphorylation of some analogues of fructose by yeast hexokinase

Abstract

Since Meyerhof separated hexokinase in a purified form from bakers’ yeast a great deal of information on the properties of this enzyme has bene obtained by numerous workers. In particular the question of the specificity of yeast hexokinase was believed to initiate hexose metabolism in the living organism, and hence the enzyme would be expected to play an important part in determining whether certain sugars could be utilized or not by yeast. Certain cases of inhibition of various metabolic processes in the living cell were found to have been caused by the specific inhibition of hexokinase.

The pattern of specificity of the substrates of hexokinase falls into two different classes. Some sugars are phosphorylated in the pyranose form and others in the furanose form. The specific requirements for pyranoses have been investigated extensively but there is relatively little information in the literature on the furanose aspect of hexokinase specificity. The object of this research was to investigate the specificity of the enzyme in respect of analogues of fructose and in particular those sugars which differ only slightly from fructofuranose at carbon-1 and carbon -2.

To this end, the chemical syntheses of the following compounds were undertaken:

1_amino_l_deoxy_D_fructose 1_deoxy_D_fructose 2.5_anhydro_D_mannitol 2.5_anhydro_D_sorbitol

Preparations of 1_amino_1_deoxy_D_fructose and 2.5_anhydro_D_sorbitol have been published, but the other two sugars are new compounds.

Part I of this thesis contains a review of the chemistry of 1_amino_1_deoxy_D_fructose, 1_deoxyketoses and 2_deoxyketoses, a report of the experimental work carried out by the author in synthesising the above mentioned compounds, and a discussion of the results obtained.

Part II contains a review of the knowledge of yeast hexokinase, a report of the experimental work carried out in investigating the effects of the synthesised fructose analogues in the hexokinase reaction, and a discussion of these results in the light of other information on the specificity of the enzyme. A systematic investigation of a spectrophotometric assay method for following hexokinase activity is included in Part II. The appendix contains the data from which the graphs and tables, shown in the thesis, have been completed.