Compartmentation protects trypanosomes from the dangerous design of glycolysis

Compartmentation protects trypanosomes from the dangerous design of glycolysis

^*Molecular Cell Physiology, BioCentrum Amsterdam, Vrije Universiteit, De Boelelaan 1087, NL-1081 HV Amsterdam, The Netherlands; ^†E. C. Slater Institute, BioCentrum Amsterdam, University of Amsterdam, Plantage Muidergracht 12, NL-1018 TV Amsterdam, The Netherlands; ^‖Research Unit for Tropical Diseases, Christian de Duve Institute of Cellular Pathology and Laboratory of Biochemistry, Université Catholique de Louvain, Avenue Hippocrate 74, B-1200 Brussels, Belgium; and ^¶Kluyver Laboratory for Biotechnology, Delft University of Technology, Julianalaan 67, NL-2628 BC Delft, The Netherlands

Communicated by Christian de Duve, Christian de Duve Institute of Cellular Pathology, Brussels, Belgium (received for review October 7, 1999)

Abstract

Unlike in other organisms, in trypanosomes and other Kinetoplastida the larger part of glycolysis takes place in a specialized organelle, called the glycosome. At present it is impossible to remove the glycosome without changing much of the rest of the cell. It would seem impossible, therefore, to assess the metabolic consequences of this compartmentation. Therefore, we here develop a computer experimentation approach, which we call computational cell biology. A validated molecular kinetic computer replica was built of glycolysis in the parasite Trypanosoma brucei. Removing the glycosome membrane in that replica had little effect on the steady-state flux, which argues against the prevalent speculation that glycosomes serve to increase flux by concentrating the enzymes. Removal of the membrane did cause (i) the sugar phosphates to rise to unphysiologically high levels, which must have pathological effects, and (ii) a failure to recover from glucose deprivation. We explain these effects on the basis of the biochemical organization of the glycosome. We conclude (i) that the glycosome protects trypanosomes from the negative side effects of the “turbo” structure of glycolysis and (ii) that computer experimentation based on solid molecular data is a powerful tool to address questions that are not, or not yet, accessible to experimentation.

Footnotes

↵ ** To whom reprint requests should be addressed. E-mail: hw{at}bio.vu.nl.
↵ ‡ Present address: Kluyver Laboratory for Biotechnology, Delft University of Technology, Julianalaan 67, NL-2628 BC Delft, The Netherlands.
↵ § Present address: TNO Prevention and Health, Gaubius Laboratory, PO Box 2215, NL-2301 CE Leiden, The Netherlands.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.030539197.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.030539197
Abbreviations:

HK,

hexokinase;

PFK,

phosphofructokinase;

Glc-6-P,

glucose 6-phosphate;

Fru-1,6-BP,

fructose 1,6-bisphosphate