Figure 3.

Implications of the "turbo" design of the glycolytic pathway. (A) The design of the glycolytic pathway, with its first steps (HXK, PFK) kept far from equilibrium by continuous investment of ATP, may lead to unrestricted accumulation of intermediates, if no tight regulation of these steps occurs by product or feed-back inhibition. (B) The compartmentation of the major part of the pathway in trypanosomes (resulting in no net ATP production inside the glycosome), may lead to a low ATP/ADP ratio sensed by HXK and PFK (and different from the ratio in the cytosol), thus keeping the activities of these enzymes under control without need for feed-back inhibition. Abbreviations: I, metabolic intermediate; S, substrate; P, product.