nitrogenase

Examples of nitrogenase in the following topics:

• Anaerobiosis and N2 Fixation

  • Nitrogen fixing bacteria have different strategies to reduce oxygen levels, which interfere with nitrogenase function.
  • Central to nitrogen fixation (N2 to NH3) are the enzymes that do the actual fixation, these are known as nitrogenases.
  • In essence, O2 binds to the iron (Fe) found in nitrogenases and blocks their ability to bind to N2.
  • To protect nitrogenases, there are mechanisms for nitrogen fixers to protect nitrogenase from oxygen in vivo.
  • Outline the various mechanisms utilized by nitrogen-fixing bacteria to protect nitrogenases from oxygen

• Nitrogenase and Nitrogen Fixation

  • Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase.
  • Nitrogenases are enzymes used by some organisms to fix atmospheric nitrogen gas (N2).
  • All nitrogenases have an iron- and sulfur-containing cofactor that includes a heterometal complex in the active site (e.g., FeMoCo).
  • Enzymes responsible for nitrogenase action are very susceptible to destruction by oxygen.

• Nitrogen Fixation Mechanism

  • The conversion of N2 to NH3 depends on a complex reaction, essential to which are enzymes known as nitrogenases.
  • Nitrogenase is made up of two soluble proteins: component I and II .
  • Component II known as Fe protein or nitrogenase reductase is composed of two copies of a single subunit.
  • Nitrogenase ultimately bonds each atom of nitrogen to three hydrogen atoms to form ammonia (NH3).
  • D) The protein complex dissociates, and nitrogenase reduces dinitrogen to ammonia and dihydrogen.

• Genetics and Regulation of N2 Fixation

  • The primary enzyme encoded by the nif genes is the nitrogenase complex which is in charge of converting atmospheric nitrogen to other nitrogen forms such as ammonia, which plants can use for various purposes.
  • Besides the nitrogenase enzyme, the nif genes also encode a number of regulatory proteins involved in nitrogen fixation.
  • In turn, NifL inhibits NifA activity, which results in the inhibition of nitrogenase formation.

• Gas Requirements

  • Often, they respire oxygen as rapidly as it is supplied, keeping the amount of free oxygen low. 3) Aerobes that require oxygen to grow, yet their nitrogenase is still debilitated if exposed to oxygen. 4) Oxygenic photosynthetic bacteria generate oxygen as a by-product of photosynthesis, yet some are able to fix nitrogen as well. 5) And finally, Anoxygenic photosynthetic bacteria that do not generate oxygen during photosynthesis as they have only a single photosystem which cannot split water.
  • In addition, nitrogenase is expressed under nitrogen limitation.

• Benzoate Catabolism

  • In PNS bacteria, hydrogen production is due to catalysis by nitrogenase.
  • Only under nitrogen-deficient conditions is nitrogenase activity sufficient to overcome uptake hydrogenase activity, resulting in net generation of hydrogen.

• The Nitrogen Cycle

  • These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia.

• Cyanobacteria

  • Thick-walled heterocysts, which contain the enzyme nitrogenase, vital for nitrogen fixation.

• Role of Microbes in Biogeochemical Cycling

  • Almost all of the nitrogen fixation that occurs on the planet is carried out by bacteria that have the enzyme nitrogenase, which combines N2 with hydrogen to produce a useful form of nitrogen (such as ammonia).