Tracking the Orchestration of the Tricarboxylic Acid Pathway in Plants, 80 Years After the Discovery of the Krebs Cycle

2017 ◽  
pp. 285-298 ◽  
Author(s):  
Guillaume Tcherkez
Keyword(s):  
Krebs Cycle ◽  
Tricarboxylic Acid ◽  
Acid Pathway

scholarly journals Succinate dehydrogenase (SDHx) mutations in pituitary tumors: could this be a new role for mitochondrial complex II and/or Krebs cycle defects?

2012 ◽  
Vol 19 (6) ◽  
pp. C33-C40 ◽  
Author(s):  
Paraskevi Xekouki ◽  
Constantine A Stratakis
Keyword(s):  
Thyroid Cancer ◽  
Succinate Dehydrogenase ◽  
Krebs Cycle ◽  
Pituitary Tumors ◽  
Tricarboxylic Acid ◽  
Genetic Defects ◽  
Disease Phenotype ◽  
Cowden Disease ◽  
Mitochondrial Complex ◽  
Complex Ii

Succinate dehydrogenase (SDH) or mitochondrial complex II is a multimeric enzyme that is bound to the inner membrane of mitochondria and has a dual role as it serves both as a critical step of the tricarboxylic acid or Krebs cycle and as a member of the respiratory chain that transfers electrons directly to the ubiquinone pool. Mutations in SDH subunits have been implicated in the formation of familial paragangliomas (PGLs) and/or pheochromocytomas (PHEOs) and in Carney–Stratakis syndrome. More recently, SDH defects were associated with predisposition to a Cowden disease phenotype, renal, and thyroid cancer. We recently described a kindred with the coexistence of familial PGLs and an aggressive GH-secreting pituitary adenoma, harboring anSDHDmutation. The pituitary tumor showed loss of heterozygosity at theSDHDlocus, indicating the possibility thatSDHD's loss was causatively linked to the development of the neoplasm. In total, 29 cases of pituitary adenomas presenting in association with PHEOs and/or extra-adrenal PGLs have been reported in the literature since 1952. Although a number of other genetic defects are possible in these cases, we speculate that the association of PHEOs and/or PGLs with pituitary tumors is a new syndromic association and a novel phenotype for SDH defects.

scholarly journals Correlation of dicarboxylic acid cycle with tricarboxylic acid cycle in highly productive pigs

2020 ◽  
Vol 58 (2) ◽  
pp. 215-225
Author(s):  
K. S. Ostrenko ◽  
V. P. Galochkina ◽  
V. О. Lemiasheuski ◽  
A. V. Agafonova ◽  
A. N. Ovcharova ◽  
...  
Keyword(s):  
Dicarboxylic Acid ◽  
Lower Layer ◽  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Krebs Cycle ◽  
Tricarboxylic Acid ◽  
Malate Synthase ◽  
The Body ◽  
Mitochondrial Enzymes ◽  
Acid Cycle

The paper is the fundamental beginning of research series aimed at understanding the processes associated with high performance in higher animals. The research aim is to study correlation of dicarboxylic acid cycle with tricarboxylic acid cycle with establishment of activity and dislocation of enzymes, confirming the hypothesis of availability and active metabolic participation of peroxisome in highly productive animals. Research was conducted on the basis of the VNIIFBiP animal vivarium in 2019 with a group of piglets of the Irish Landrace breed (n = 10). After slaughter at the age of 210 days, the nuclear (with large tissue particles), mitochondrial and postmitochondrial fractions of the liver were studied with assessment of succinate dehydrogenase and activity of other dehydrogenes of the Krebs cycle. It was found that peroxisomes act as universal agents of communication and cooperation, and microtelets are able to generate various chemical signals that carry information, to control and arrange a number of mechanisms in the metabolic processes in the body. Despite the fact that the Krebs cycle dehydrogenases are considered mitochondrial enzymes, the experiment showed an increase in activity of priruvate dehydrogenase (P > 0.1), isocitrate dehydrogenase (0.1 > P > 0.05) and malate dehydrogenase (0.1 > P > 0.05), which, when comparing the mitochondrial and postmitochondrial fractions, indicates a higher activity of peroxisomal fractions. The peroxisome localization place is the postmitochondrial fraction, and the lower layer contains larger peroxisomes to a greater extent, while the upper layer contains smaller ones. It was found that indicator enzymes of glyoxylate cycle isocitratliase and malate synthase exhibit catalytic activity in the peroxisomal fraction of liver of highly productive pigs. The obtained data on functioning of key glyoxylate cycle enzymes and their intracellular compartmentalization in highly productive pigs allow learning more about the specifics of metabolism and its regulation processes. Application of this knowledge in practice opens up prospects for rationalizing the production of livestock products of increased quantity, improved quality with less feed, labor and financial resources spent.

Computer simulation of metabolism in pyruvate-perfused rat heart. II. Krebs cycle

1979 ◽  
Vol 237 (3) ◽  
pp. R159-R166 ◽  
Author(s):  
M. C. Kohn ◽  
M. J. Achs ◽  
D. Garfinkel
Keyword(s):  
Redox Potential ◽  
Rat Heart ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Krebs Cycle ◽  
Coordinated Control ◽  
Work Load ◽  
Metabolic Model ◽  
Tricarboxylic Acid ◽  
Perfused Rat Heart

A realistic metabolic model of the tricarboxylic acid cycle in the perfused rat heart was constructed to help explain the sequence of biochemical events regulating the metabolism of exogenous pyruvate following a large increase in work load. The unchelated Mg2+ level was the most important controlling factor. The resulting mixture of chelated and unchelated nucleotides and tribasic acids effected coordinated control of citrate synthase, aconitase, isocitrate dehydrogenase, succinyl CoA synthetase, fumarase, and nucleoside diphosphokinase, because Mg2+-chelates are generally substrates whereas unchelated species are inhibitors. Succinate dehydrogenase is largely controlled by the ubiquinone redox potential. The fluxes through alpha-ketoglutarate and malate dehydrogenases are largely dependent on thepyridine nucleotide redox potential, but the succinyl CoA-to-CoASH ratio strongly affects the former enzyme as well. The model predicts an accumulation of succinate during the transition to higher work output.

The tricarboxylic acid pathway in Desulfovibrio

1977 ◽  
Vol 23 (7) ◽  
pp. 916-921 ◽  
Author(s):  
A. J. Lewis ◽  
J. D. A. Miller
Keyword(s):  
Yeast Extract ◽  
Malic Enzyme ◽  
Pyruvate Carboxylase ◽  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Dicarboxylic Acids ◽  
Tricarboxylic Acid ◽  
Desulfovibrio Vulgaris ◽  
Acid Cycle ◽  
Acid Pathway

Strains of two species of Desulfovibrio were examined for enzymes of the tricarboxylic acid cycle and related pathways. Pyruvate carboxylase (EC 6.4.1.1) is present, and α-ketoglutarate is formed via the tricarboxylic acids. Glutamate, but not succinyl-CoA, arises from α-ketoglutarate. A pathway exists from pyruvate by malic enzyme (EC 1.1.1.39) activity to malate, then fumarate and succinate, again with no evidence of succinyl-CoA formation. The enzymes concerned with metabolism of these dicarboxylic acids show greater activity in the strains that can grow by fumarate dismutation. Glutamate (or glutamine), α-ketoglutarate, and yeast extract repress the enzymes that metabolize the tricarboxylic acids. There appears to be no glyoxylate cycle in Desulfovibrio vulgaris or D. desulfuricans.

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