The enzyme citrate synthase (E.C. 126.96.36.199 ) exists in nearly all living cells and stands as a pace-making enzyme in the first step of the Citric Acid Cycle (or Krebs Cycle). Citrate synthase is localized within eukaryotic cells in the mitochondrial matrix, but is encoded by nuclear DNA rather than mitochondrial. It is synthesized using cytoplasmic ribosomes, then transported into the mitochondrial matrix. Citrate synthase is commonly used as a quantitative enzyme marker for the presence of intact mitochondria.
Citrate synthase catalyzes the condensation reaction of the two-carbon acetate residue from acetyl coenzyme A and a molecule of four-carbon oxaloacetate to form the six-carbon citrate. Oxaloacetate will be regenerated after the completion of one round of the Krebs Cycle.
acetyl-CoA + oxaloacetate + H2O → citrate + CoA-SH
Oxaloacetate is the first substrate to bind to the enzyme. This induces the enzyme to change its conformation, and creates a binding site for the acetyl-CoA. Only when this citroyl-CoA has formed will another conformational change cause thioester hydrolysis and release coenzyme A. This ensures that the energy released from the thioester bond cleavage will drive the condensation.
Other articles related to "citrate synthase, synthase, citrate":
... α-ketoglutarate dehydrogenase, and citrate synthase, increase in expression and activity in response to exercise ... of AMPK increases cytochrome c and δ-aminolevulinate synthase (ALAS), a rate-limiting enzyme involved in the production of heme ... Malate dehydrogenase and succinate dehydrogenase also increase, as well as citrate synthase activity, in rats treated with AICAR injections ...
... pyruvate dehydrogenase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and also citrate synthase ... 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 ...
... In enzymology, a citrate (Re)-synthase (EC 188.8.131.52) is an enzyme that catalyzes the chemical reaction acetyl-CoA + H2O + oxaloacetate citrate + CoA The 3 substrates of this enzyme are acetyl-CoA, H2O ... Other names in common use include (R)-citrate synthase, Re-citrate-synthase, and citrate oxaloacetate-lyase ...
... These reactions are performed by fatty acid synthase II (FASII), which in general contain multiple enzymes that act as one complex ... fungi, these same reactions occur on fatty acid synthase I (FASI), a large dimeric protein that has all of the enzymatic activities required to create a fatty acid ... formed, it can undergo a number of modifications, in particular by fatty acid synthase III (FASIII), which uses 2 carbon molecules to elongate preformed fatty acids ...