Tricarboxylate cycle regulation

Arsan, O.M. (1986). The role of water temperature in regulation of die processes of glycolysis and the tricarboxylic cycle in fish (In Russian). Gydmbiologicheskii Zhumal 22(5), 71-74. 

Coenzyme availability can also often have a limiting effect (5). If the coenzyme is regenerated by a second, independent metabolic pathway, the speed of the second pathway can limit that of the first one. For example, glycolysis and the tricarboxylic acid cycle are mainly regulated by the availability of NAD" (see p. 146). Since NAD is regenerated by the respiratory chain, the latter indirectly controls the breakdown of glucose and fatty acids (respiratory control, see p. 144). 

The most important regulator of p-oxida-tion is the NAD /NADH+H ratio. If the respiratory chain is not using any NADH+H, then not only the tricarboxylic acid cycle (see p. 136) but also p-oxidation come to a standstill due to the lack of NADT... 

How could the activities of the kinase and phosphorylase be regulated so as to control the entry of pyruvate into the tricarboxylic acid cycle ... 

B. S. Sacktor and E. Wormser-Shavit, Regulation of metabolism in working muscle in vivo. I. Concentrations of some glycolytic, tricarboxylic acid cycle, and amino acid intermediates in insect flight muscle during flight, J. Biol. Chem., 241 (1966) 624-631. 

To obtain citric acid as the metabolic product again requires interference with the normal Krebs tricarboxylic acid cycle in such a way that citric acid metabolism is blocked. Usually this is achieved by careful regulation of concentrations of trace metals available as coenzymes to the various enzyme pathways used by A. niger, so that some of these are rendered ineffective (are blocked). 

Buchanan, R. L. and Lewis, D. F. 1984. Regulation of aflatoxin biosynthesis Effect of glucose on the activities of various glycolytic enzymes. Appl. Environ. Microbiol. 48, 306-310. Buchanan, R. L., Federowicz, D., and Stahl, H. G. 1985. Activities of tricarboxylic acid cycle... 

Despite the thousands of secondary metabolites made by microorganisms, they are synthesized from only a few key precursors in pathways that comprise a relatively small number of reactions and which branch off from primary metabolism at a limited number of points. Acetyl-CoA and propionyl-CoA are the most important precursors in secondary metabolism, leading to polyketides, terpenes, steroids, and metabolites derived from fatty acids. Other secondary metabolites are derived from intermediates of the shikimic acid pathway, the tricarboxylic acid cycle, and from amino acids. The regulation of the biosynthesis of secondary metabolites is similar to that of the primary processes, involving induction, feedback regulation, and catabolite repression [6]. 

In class VI are ADP-Glc PPases from anaerobic bacteria Rhodospirillum, capable of growing in either hetero-trophic conditions in the dark or autotrophic conditions in the light under anoxygenic photosynthesis (Table 1). These organisms cannot catabolize glucose but grow very well on pyruvate and tricarboxylic acid cycle (TCA) intermediates. ADP-Glc PPases from class VI are specifically regulated by pyruvate (Table... 

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