Regulation of the pentose phosphate cycle in bass (Dicentrarchus labrax L.) liver.

The influence in the activities of the glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase produced by the ratio changes NADPH/NADP is studied. The intracellular ratios of 20 and 10 are enough to achieve total inhibition of these two enzymes, respectively. Measurements of a number of metabolic intermediates show that the concentrations of Krebs cycle compounds are higher than those of glycolytic pathway metabolites. From a consideration of these values, the regulation of the pentose phosphate cycle mainly by the intracellular NADPH/NADP ratio, is discussed.