ATP synthase

Examples of ATP synthase in the following topics:

• F10 ATP Synthase

  • ATP synthase is an important enzyme that provides energy for the cell to use through the synthesis of adenosine triphosphate (ATP).
  • The overall reaction sequence is: ATP synthase + ADP + Pi → ATP Synthase + ATP
  • Oligomycin, an antibiotic, is able to inhibit the FO unit of ATP synthase.
  • E. coli ATP synthase is the simplest known form of ATP synthase, with 8 different subunit types.
  • Discuss the structure and function of ATP synthase, including the F1 and FO components

• Chemiosmosis and Oxidative Phosphorylation

  • Similarly, hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through a membrane protein called ATP synthase.
  • Chemiosmosis is used to generate 90 percent of the ATP made during aerobic glucose catabolism.
  • The production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation.
  • In oxidative phosphorylation, the hydrogen ion gradient formed by the electron transport chain is used by ATP synthase to form ATP.
  • ATP synthase is a complex, molecular machine that uses a proton (H+) gradient to form ATP from ADP and inorganic phosphate (Pi).

• Processes of the Light-Dependent Reactions

  • Cytochrome b6f complex and ATP synthase are also major protein complexes in the thylakoid membrane that work with the photosystems to create ATP and NADPH.
  • Cytochrome b6f and ATP synthase work together to create ATP.
  • The energy released by the hydrogen ion stream allows ATP synthase to attach a third phosphate group to ADP, which forms ATP .
  • This flow of hydrogen ions through ATP synthase is called chemiosmosis because the ions move from an area of high to an area of low concentration through a semi-permeable structure.
  • ATP synthase uses this electrochemical gradient to make ATP.

• Respiration and Proton Motive Force

  • Aerobic reactions require oxygen for ATP generation.
  • They are able to do this with the help of the solar-driven enzyme bacteriorhodopsin, which is used to drive the molecular motor enzyme ATP synthase to make the necessary conformational changes required to synthesize ATP.
  • By running ATP synthase in reverse, proton gradients are also made by bacteria and are used to drive flagella.
  • The F1FO ATP synthase is a reversible enzyme.
  • In respiring bacteria under physiological conditions, ATP synthase, in general, runs in the opposite direction.

• Proton Reduction

  • This potential energy is used for the synthesis of ATP by phosphorylation.
  • In respiring bacteria under physiological conditions, ATP synthase, in general, runs in the opposite direction, creating ATP while using the proton motive force created by the electron transport chain as a source of energy.
  • The same process takes place in the mitochondria, where ATP synthase is located in the inner mitochondrial membrane, so that F1 part sticks into the mitochondrial matrix where ATP synthesis takes place.
  • A proton motive force or pmf drives protons down the gradient (across the membrane) through the proton channel of ATP synthase.
  • Instead, it only uses substrate-level phosphorylation to produce ATP.

• Secondary Active Transport

  • Unlike in primary active transport, in secondary active transport, ATP is not directly coupled to the molecule of interest.
  • While this process still consumes ATP to generate that gradient, the energy is not directly used to move the molecule across the membrane, hence it is known as secondary active transport.
  • This secondary process is also used to store high-energy hydrogen ions in the mitochondria of plant and animal cells for the production of ATP.
  • The potential energy that accumulates in the stored hydrogen ions is translated into kinetic energy as the ions surge through the channel protein ATP synthase, and that energy is used to convert ADP into ATP.

• Photoautotrophs and Photoheterotrophs

  • Phototrophs are organisms that use light as their source of energy to produce ATP and carry out various cellular processes.
  • All phototrophs either use electron transport chain or direct proton pumping to establish an electro-chemical gradient utilized by ATP synthase to provide molecular energy for the cell.
  • Photoheterotrophs produce ATP through photophosphorylation but use environmentally obtained organic compounds to build structures and other bio-molecules.

• Nanoarchaeum and Aciduliprofundum

  • The organism's ability to produce its own ATP is also in question.
  • It does have five subunits of an ATP synthase as well as pathways for oxidative deamination.
  • Whether it obtains energy from biological molecules imported from Ignicoccus, or whether it receives ATP directly is currently unknown.

• The Reverse TCA Cycle

  • ATP citrate lyase is one of the key enzymes that function in reverse TCA.
  • ATP citrate lyase is the enzyme responsible for cleaving citrate into oxaloacetate and acetyl CoA.
  • 4) succinate is converted to succinyl-CoA (ATP is hydrolyzed to ADP+Pi)
  • 5) succincyl CoA is converted to alpha-ketoglutarate via an alpha-ketoglutarate synthase (reduction of carbon dioxide occurs and oxidation of coenzyme A)
  • 8) ATP citrate lyase is then used to convert citrate to oxaloacetate and acetyl CoA (ATP is hydrolyzed to ADP and Pi).

• Purine and Pyrimidine Synthesis

  • UDP can also be converted to CTP by CTP synthase cytidine 5'triphosphate (CTP)using glutamine and ATP.The first three enzymes are all coded by the same gene in Metazoa (CAD).
  • CTP synthase (or CTP synthetase) is an enzyme involved in pyrimidine biosynthesis.
  • CTP synthase is activated by GTP, a purine.
  • CTP synthase is inhibited by reversible by CTP and irreversible for example by the glutamine analogon DON.
  • The following human genes encode proteins that possess CTP synthase activity: