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Related Concept Videos

Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

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Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme...
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Carbonyl compounds and primary amines undergo reductive amination first to produce imines, followed by secondary amines in the same reaction mixture, using selective reducing agents like sodium cyanoborohydride or sodium triacetoxyborohydride. Reductive amination produces different degrees of substitution of amines depending on the starting amine substrate.
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Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
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Like all living organisms, plants require organic and inorganic nutrients to survive, reproduce, grow and maintain homeostasis. To identify nutrients that are essential for plant functioning, researchers have leveraged a technique called hydroponics. In hydroponic culture systems, plants are grown—without soil—in water-based solutions containing nutrients. At least 17 nutrients have been identified as essential elements required by plants. Plants acquire these elements from the...
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Phase I biotransformation reductive reactions are chemical processes that modify drugs by introducing or revealing polar functional groups via reduction. Enzymes called reductases catalyze these reactions, playing a pivotal role in drug metabolism by transforming lipophilic drugs into more polar, water-soluble metabolites for easy excretion. An essential type of reductive reaction is the carbonyl group reduction, where aldehydes and ketones are reduced to alcohols. An example is the...
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Measuring Fluxes of Mineral Nutrients and Toxicants in Plants with Radioactive Tracers
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Studies on nitrite reductase in barley.

W F Bourne1, B J Miflin

  • 1Department of Plant Science, The University, NEI 7RU, Newcastle upon Tyne, U.K..

Planta
|January 29, 2014
PubMed
Summary

Barley seedlings

Area of Science:

  • Plant biochemistry and molecular biology.
  • Enzyme kinetics and purification.

Background:

  • Nitrite reductase (NiR) is a key enzyme in nitrate assimilation in plants.
  • Understanding NiR characteristics in different plant tissues is crucial for plant physiology research.

Purpose of the Study:

  • To purify and characterize nitrite reductase from barley seedlings.
  • To investigate the substrate specificity and regulatory factors of barley NiR.

Main Methods:

  • Enzyme purification using ammonium sulfate precipitation and gel filtration.
  • Enzyme activity assays with various electron donors and inhibitors.
  • Comparison of NiR properties between leaf and root tissues.

Main Results:

  • Nitrite reductase was purified 50-60 fold from barley seedlings.

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  • Leaf and root nitrite reductases exhibited similar characteristics.
  • The root enzyme utilized reduced methyl viologen, ferredoxin, or an endogenous cofactor.
  • Nitrate-rich growth significantly increased enzyme activity in both tissues.
  • Nitrite reductase activity was distinct from sulfite reductase activity and not due to microbial contamination.
  • In vitro assays showed inhibition by 2,4-dinitrophenol but not arsenate.

    • Conclusions:

    • Barley seedlings possess a nitrite reductase with consistent properties across leaf and root tissues.
    • Enzyme activity is inducible by nitrate and can utilize multiple electron donors.
    • The enzyme's distinctness from sulfite reductase and insensitivity to microbial contamination were confirmed.