Pyruvate kinase

About: Pyruvate kinase is a research topic. Over the lifetime, 5683 publications have been published within this topic receiving 180020 citations. The topic is also known as: ATP:pyruvate 2-O-phosphotransferase & phosphoenolpyruvate kinase.

Different signals control the activation of glycolysis in the yeast Saccharomyces cerevisiae

Abstract: The glycolytic pathway in Saccharomyces cerevisiae is activated by fermentable sugars at several steps. Mutants with deletions of genes coding for enzymes of the upper part of glycolysis were used to characterize the triggering mechanisms. Synthesis of fructose-2,6-bisphophate is catalysed by two 6-phosphofructo-2-kinase isoenzymes, one of which is activated by fermentable sugars while synthesis of the second enzyme is induced (Kretschmer and Fraenkel, 1991). Increase in the level of fructose-2,6-bisphosphate is demonstrated to depend on an internal metabolite upstream of the phosphoglucose isomerase reaction. The signalling process correlates with distinct temporal changes in the concentration of glucose-6-phosphate but not with its absolute level, indicating an adaptational mechanism. It is independent of the uptake and phosphorylation systems used by different sugars. Interestingly, this increase, although delayed, could also be observed in strains lacking the rapid cAMP increase after sugar addition which is thought to be responsible for the activating process. Synthesis of glucose-6-P and fructose-6-P is needed for the complete induction of pyruvate kinase and inactivation of fructose-1,6-bisphosphatase. On the other hand, induction of pyruvate decarboxylase depends mainly on a signal in the lower part of glycolysis.

Maximum activities and effects of fructose bisphosphate on pyruvate kinase from muscles of vertebrates and invertebrates in relation to the control of glycolysis.

Abstract: 1. Comparison of the maximum activities of pyruvate kinase with those of phosphofructokinase in a large number of muscles from invertebrates and vertebrates indicates that, in general, in any individual muscle, the activity of pyruvate kinase is only severalfold higher than that of phosphofructokinase. This is consistent with the suggestion, based on mass-action ratio data, that the pyruvate kinase reaction is non-equilibrium in muscle. However, the range of activities of pyruvate kinase in these muscles is considerably larger than that of phosphofructokinase. This difference almost disappears if the enzyme activities from muscles that are known to possess an anaerobic ;succinate pathway' are excluded. It is suggested that, in these muscles, phosphofructokinase provides glycolytic residues for both pyruvate kinase (i.e. glycolysis) and phosphoenolpyruvate carboxykinase (i.e. the succinate pathway). This is supported by a negative correlation between the activity ratio, pyruvate kinase/phosphofructokinase, and the activities of nucleoside diphosphokinase in these muscles, since high activities of nucleoside diphosphokinase are considered to indicate the presence of the succinate pathway. 2. The effect of fructose bisphosphate on the activities of pyruvate kinase from many different muscles was studied. The stimulatory effect of fructose bisphosphate appears to be lost whenever an efficient system for supply of oxygen to the muscles is developed (e.g. insects, squids, birds and mammals). This suggests that activation of pyruvate kinase is important in the co-ordinated regulation of glycolysis in anaerobic or hypoxic conditions, when the change in glycolytic flux during the transition from rest to activity needs to be large in order to provide sufficient energy for the contractile activity. However, lack of this effect in the anaerobic muscles of the birds and mammals suggests that another metabolic control may exist for avian and mammalian pyruvate kinase in these muscles.

Roles of pyruvate kinase and malic enzyme in Corynebacterium glutamicum for growth on carbon sources requiring gluconeogenesis.

Abstract: In many bacteria, pyruvate kinase serves a well-defined function in glycolysis, catalyzing an ATP-generating reaction. However, its role during growth on carbon sources requiring glucoeneogenesis is less well investigated. We analyzed a defined pyruvate kinase gene (pyk) deletion mutant of Corynebacterium glutamicum, which is unable to grow on ribose as sole carbon source. Unexpectedly, the pyk deletion mutant was also unable to grow on acetate or citrate as sole carbon sources unless low amounts of pyruvate were added to the growth medium. A spontaneous suppressor mutant of the pyk deletion strain that regained the ability to grow on acetate was isolated. DNA microarray experiments revealed increased expression of the malic enzyme gene malE. The point mutation upstream of malE identified in this mutant was responsible for the loss of carbon-source-dependent regulation, as revealed by transcriptional fusion analysis. Overexpression of malE was sufficient to restore growth of the pyk deletion strain on acetate or citrate. The requirement of increased malic enzyme levels to re-route the carbon flux at the interface between glycolysis, gluconeogenesis and the tricarboxylic acid cycle in order to compensate for the absence of pyruvate kinase indicates a metabolic flux bifurcation at the metabolic node phosphoenolpyruvate. Whereas during growth of C. glutamicum on acetate or citrate most of the phosphoenolpyruvate generated from oxaloacetate is metabolized in gluconeogenesis, a fraction is converted by pyruvate kinase in the glycolytic direction to sustain proper pyruvate availability for biomass synthesis.