The regulation of the pentose phosphate pathway: Remember Krebs.

The changes in gene expression and posttranslational modifications of enzymes are comprised in the concept of "coarse control" of the oxidative phase of the pentose phosphate pathway. However, these changes are slow in its implementation. The defensive mechanism against oxidative stress requires a most rapid response, impossible to achieve with coarse regulation systems. Recently, it has been suggested that a quick acceleration mechanism of G6PD activity could be produced by the reduction of NADPH-inhibition of G6PD. The hypothesis opens new ways on possible mechanisms for rapid modulation that could be in accordance with results obtained in the 70s by Krebs. These results seemed outdated in view of the subsequent research. However, they deserve to be re-assessed at present.