Accessibility of Trypanosoma bruceiprocyclic glycosomal enzymes to labeling agents of various sizes and charges

The high efficiency of glycolysis in Trypanosoma bruceihas been attributed to impermeability of the glycosomal membrane to most metabolites. However, the strong stimulation of the glycolytic rate by exogenous metabolites and coenzymes in intact glycosomes is only compatible with their accessibility to the internal space. The accessibility of glycosomal enzymes to protein labeling agents of varying charge and size has been investigated. The results show that the glycosomal membrane is permeable to small molecules of the size of metabolites, but impermeable to larger molecules.