Title: OGDH
Content:  This subunit, known as E1o, catalyzes a rate-limiting step in the citric acid cycle and lies far from equilibrium; the total change in Gibbs free energy is ΔG = −33 kJ/mol. The significant energy change makes it a crucial point of regulation not only for the citric acid cycle, but also for the entire cellular respiration pathway. As such, E1o is inhibited by both NADH and Succinyl-CoA via non competitive feedback inhibition.
Title: Hans Krebs (biochemist)
Content:  Krebs continued to add more details to his citric acid cycle. The discovery of acetyl-CoA in 1947 by Fritz Albert Lipmann was another major contribution. However, this new discovery posed a problem in his classic reaction. In 1957 he, with Hans Kornberg, found that there were additional crucial enzymes. One was malate synthase, which condenses acetate with glyoxylate to form malate, and the other was isocitrate lyase, which provides glyoxylate for the reaction by cleaving it from isocitrate. These two reactions did not follow the normal citric acid cycle, and hence the pathway was named the glyoxylate bypass of the citric acid cycle, but is now known as the glyoxylate cycle.
Title: Citric acid cycle
Content:  cycle intermediate, succinyl-CoA. These molecules are an important component of the hemoproteins, such as hemoglobin, myoglobin and various cytochromes. During gluconeogenesis mitochondrial oxaloacetate is reduced to malate which is then transported out of the mitochondrion, to be oxidized back to oxaloacetate in the cytosol. Cytosolic oxaloacetate is then decarboxylated to phosphoenolpyruvate by phosphoenolpyruvate carboxykinase, which is the rate limiting step in the conversion of nearly all the gluconeogenic precursors (such as the glucogenic amino acids and lactate) into glucose by the liver and kidney. Because the citric acid cycle is involved in both catabolic and anabolic processes, it is known as an amphibolic pathway. Evan M.W.Duo
Title: Citric acid cycle
Content:  dehydrogenase, and also citrate synthase. Acetyl-coA inhibits pyruvate dehydrogenase, while succinyl-CoA inhibits alpha-ketoglutarate dehydrogenase and citrate synthase. When tested in vitro with TCA enzymes, ATP inhibits citrate synthase and α-ketoglutarate dehydrogenase; however, ATP levels do not change more than 10% in vivo between rest and vigorous exercise. There is no known allosteric mechanism that can account for large changes in reaction rate from an allosteric effector whose concentration changes less than 10%. Citrate is used for feedback inhibition, as it inhibits phosphofructokinase, an enzyme involved in glycolysis that catalyses formation of fructose 1,6-bisphosphate, a precursor of pyruvate. This prevents a 
Title: Branched-chain alpha-keto acid dehydrogenase complex
Content:  The branched-chain α-ketoacid dehydrogenase complex (BCKDC or BCKDH complex) is a multi-subunit complex of enzymes that is found on the mitochondrial inner membrane. This enzyme complex catalyzes the oxidative decarboxylation of branched, short-chain alpha-ketoacids. BCKDC is a member of the mitochondrial α-ketoacid dehydrogenase complex family comprising pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, key enzymes that function in the Krebs cycle.
Title: Citrate synthase family
Content:  In molecular biology, the citrate synthase family of proteins includes the enzymes citrate synthase, and the related enzymes 2-methylcitrate synthase and ATP citrate lyase. Citrate synthase is a member of a small family of enzymes that can directly form a carbon-carbon bond without the presence of metal ion cofactors. It catalyses the first reaction in the Krebs' cycle, namely the conversion of oxaloacetate and acetyl-coenzyme A into citrate and coenzyme A. This reaction is important for energy generation and for carbon assimilation. The reaction proceeds via a non-covalently bound citryl-coenzyme A intermediate in a 2-step process (aldol-Claisen condensation followed by the hydrolysis of citryl-CoA). Citrate synthase enzymes are found in two distinct structural types: type I enzymes (found 
Title: BCKDHA
Content:  The second major step in the catabolism of the branched-chain amino acids, isoleucine, leucine, and valine, is catalyzed by the branched-chain alpha-keto acid dehydrogenase complex (BCKD; EC 1.2.4.4), an inner-mitochondrial enzyme complex that consists of 3 catalytic components: a heterotetrameric (alpha2, beta2) branched-chain alpha-keto acid decarboxylase (E1), a homo-24-meric dihydrolipoyl transacylase (E2; MIM 248610), and a homodimeric dihydrolipoamide dehydrogenase (E3; MIM 238331). The reaction is irreversible and constitutes the first committed step in BCAA oxidation. The complex also contains 2 regulatory enzymes, a kinase and a phosphorylase. The BCKDHA gene encodes the alpha subunit of E1, and the BCKDHB gene (MIM 248611) encodes the beta subunit of E1.[supplied by OMIM] The normal function of the BCKDHA gene is 
Title: Hans Krebs (biochemist)
Content:  In 1932 Krebs worked out the outlines of the urea cycle with a medical student Kurt Henseleit at the university of Freiburg. While working at the Medical Clinic of the University of Freiburg, Krebs met Kurt Henseleit, with whom he investigated the chemical process of urea formation. In 1904, two Germans A. Kossel and H. D. Dakin had shown that arginine could be hydrolysed by the enzyme arginase to form ornithine and urea in inorganic reaction. Based on this reaction, Krebs and Henseleit postulated that in living cells, similar reaction could occur, and that ornithine and citrulline could be the intermediate reactions. Krebs started working on the possible method for the synthesis of arginine. Using his Warburg manometer, he mixed a slice of liver with purified ornithine and citrulline. He found that citrulline acted as a catalyst in the metabolic reactions of urea from ammonia and carbon dioxide. He and Henseleit published their discovery in 1932. Thus the urea cycle (or "ornithine cycle") was established, and it was the first metabolic cycle to be discovered.
Title: Biological carbon fixation
Content: Oxaloacetate to malate, using NADH + H+ Fumarate to succinate, catalyzed by an oxidoreductase, Fumarate reductase Succinate to succinyl-CoA, an ATP dependent step Succinyl-CoA to alpha-ketoglutarate, using one molecule of CO2 Alpha-ketoglutarate to isocitrate, using NADPH + H+ and another molecule of CO2 Citrate converted into oxaloacetate and acetyl-CoA, this is an ATP dependent step and the key enzyme is the ATP citrate lyase The reverse Krebs cycle, also known as reverse TCA cycle (rTCA) or reductive citric acid cycle, is an alternative to the standard Calvin-Benson cycle for carbon fixation. It has been found in strict anaerobic or microaerobic bacteria (as Aquificales) and anaerobic archea. It was discovered by Evans, Buchanan and Arnon in 
Title: Enzyme kinetics
Content:  The study of enzyme kinetics is important for two basic reasons. Firstly, it helps explain how enzymes work, and secondly, it helps predict how enzymes behave in living organisms. The kinetic constants defined above, KM and Vmax, are critical to attempts to understand how enzymes work together to control metabolism. Making these predictions is not trivial, even for simple systems. For example, oxaloacetate is formed by malate dehydrogenase within the mitochondrion. Oxaloacetate can then be consumed by citrate synthase, phosphoenolpyruvate carboxykinase or aspartate aminotransferase, feeding into the citric acid cycle, gluconeogenesis or aspartic acid biosynthesis, respectively. Being able to predict how much oxaloacetate goes into which pathway requires knowledge of the concentration of oxaloacetate as well as the concentration and kinetics of each of these enzymes. This aim of predicting the behaviour of metabolic pathways reaches its most complex expression in the synthesis of huge amounts of kinetic and gene expression data into mathematical models of entire organisms. Alternatively, one useful simplification of the metabolic modelling problem is to ignore the underlying enzyme kinetics and only rely on information about the reaction network's stoichiometry, a technique called flux balance analysis.

Question: what is the rate limiting enzyme of kreb's cycle?
Answer: Isocitrate dehydrogenase.