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The activities of phosphorylase, hexokinase, phosphofructokinase, lactate dehydrogenase and the glycerol 3-phosphate dehydrogenases in muscles from vertebrates and invertebrates.
The enzyme activities from insect flight muscle confirm and extend much of the earlier work and indicate the type of fuel that can support insect flight and the maximum activity of hexokinase was found to be higher in red than in white vertebrate muscle. Expand
Glutamine metabolism in lymphocytes: its biochemical, physiological and clinical importance.
- E. Newsholme, B. Crabtree, M. Ardawi
- Biology, Medicine
- Quarterly journal of experimental physiology
- 10 October 1985
The role of the high rate of glutaminolysis in lymphocytes and other rapidly dividing cells may be identical to that of glycolysis: the high rates provide ideal conditions for the precise and sensitive control of the rate of use of the intermediates of these pathways for biosynthesis when required. Expand
The role of high rates of glycolysis and glutamine utilization in rapidly dividing cells
It is suggested that, in rapidly dividing ceils, high rates of glycolysis and glutaminolysis are required not for energy or precursor provision per se but for high sensitivity of the pathways involved in the use of precursors for macromolecular synthesis to specific regulators to permithigh rates of proliferation when required for example, in lymphocytes in response to a massive infection. Expand
Substrate cycles in metabolic regulation and in heat generation.
The relationship between near-equilibrium reactions and substrate cycles is emphasized, since this provides a basis for the derivation of a function describing in precise quantitative terms the factors governing the amplification provided by substrate cycles in metabolic regulation. Expand
Maximum catalytic activity of some key enzymes in provision of physiologically useful information about metabolic fluxes.
The activities of fructose diphosphatase in flight muscles from the bumble-bee and the role of this enzyme in heat generation.
- E. Newsholme, B. Crabtree, S. J. Higgins, S. D. Thornton, C. Start
- Chemistry, Medicine
- The Biochemical journal
- 1 June 1972
It is proposed that both fructose diphosphatase and phosphofructokinase are simultaneously active and catalyse a cycle between fructose 6-phosphate and fructose dPhosphate in resting bumble-bee flight muscle to produce continuous hydrolysis of ATP, with the release of energy as heat, which would help to maintain the thoracic temperature during rest periods at a level adequate for flight. Expand
The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in muscles from vertebrates and invertebrates.
Pyruvate carboxylase may be present in insect flight muscle for the provision of oxaloacetate to support the large increase in activity of the tricarboxylic acid cycle which occurs when an insect takes flight. Expand
Substrate cycles: their role in improving sensitivity in metabolic control
Experimental support is provided for the view that cycles improve sensitivity in metabolic regulation by increasing the rates of four cycles. Expand
Use of enzyme activities as indices of maximum rates of fuel utilization.
It can be shown theoretically and experimentally that the maximum activities in vitro of enzymes that catalyse near-equilibrium reactions in vivo must be considerably higher than the maximum flux… Expand
The activities of proline dehydrogenase, glutamate dehydrogenase, aspartate-oxoglutarate aminotransferase and alanine-oxoglutarate aminotransferase in some insect flight muscles.
The flavoprotein-linked enzyme proline dehydrogenase is the first enzyme of the proline oxidation pathway and therefore its activity should be limiting for the operation of this pathway (see Krebs, 1964), and to this end its activity has been measured in the flight muscles of various insects. Expand