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Related Concept Videos

Urea Cycle01:23

Urea Cycle

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The urea cycle describes how liver cells convert ammonia to urea. Ammonia is a toxic waste product of protein catabolism. Land animals must convert ammonia into the less toxic urea which can be safely eliminated by the kidneys through urine. Marine animals excrete ammonia directly, and the surrounding water dilutes the ammonia to safe levels.
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Alkylation of β-Ketoester Enolates: Acetoacetic Ester Synthesis01:07

Alkylation of β-Ketoester Enolates: Acetoacetic Ester Synthesis

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Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and β-keto esters. The reaction occurs in the presence of an alkoxide base that abstracts the acidic proton of the β-keto esters. The step results in an enolate ion which is doubly stabilized. The enolate then reacts with an alkyl halide via the SN2 process to produce an alkylated ester intermediate with a new C–C bond. The hydrolysis of the intermediate, followed by acidification, results in an...
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Amides to Carboxylic Acids: Hydrolysis01:28

Amides to Carboxylic Acids: Hydrolysis

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Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
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Fates of Pyruvate01:20

Fates of Pyruvate

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Pyruvate is the end product of glycolysis, where glucose is oxidized to pyruvate, simultaneously reducing NAD+ to NADH. Two molecules of ATP are also produced by substrate-level phosphorylation.
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
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Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis01:13

Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis

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Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
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Pyruvate Oxidation01:15

Pyruvate Oxidation

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After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure that pyruvate can enter the next metabolic pathway so that energy stored in the pyruvate molecules can be harnessed by the cells.
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
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Related Experiment Video

Updated: May 13, 2025

Direct Detection of the Acetate-forming Activity of the Enzyme Acetate Kinase
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Urease in acetogenic Lachnospiraceae drives urea carbon salvage in SCFA pools.

Isaac J Firth1, Marissa A R Sim1, Bradley G Fitzgerald1

  • 1Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada.

Gut Microbes
|April 15, 2025
PubMed
Summary
This summary is machine-generated.

Health-associated gut bacteria, Blautia, utilize urea to produce short-chain fatty acids (SCFAs) and incorporate urea carbon into metabolites. This unique mechanism differs from ureolytic pathogens, highlighting urea

Keywords:
AnaerostipesBlautiaLachnospiraceaeUreaseacetateacetogenesisacidificationbutyratecross-feedingmicrobiotashort-chain fatty acidsureaurea-derived acetate production

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Area of Science:

  • Microbiology
  • Gut Microbiome Research
  • Metabolic Engineering

Background:

  • The gut microbiota produces short-chain fatty acids (SCFAs) and acidifies the colon, inhibiting pathogens.
  • The mechanisms by which gut microbes resist these stresses, particularly pH stress, are not fully understood.
  • The Lachnospiraceae family, including the genus Blautia, are SCFA producers with diverse genomic capabilities and varying acidification capacities.

Purpose of the Study:

  • To investigate how Lachnospiraceae tolerate pH stress.
  • To determine the role of urease in the physiology of Lachnospiraceae.
  • To elucidate the unique utilization of urea by Blautia and its impact on gut microbial metabolism.

Main Methods:

  • Random forest modeling to identify factors associated with acidification.
  • Culturing and metabolic analysis of urease-encoding Blautia.
  • Comparative analysis with ureolytic pathogens Klebsiella pneumoniae and Proteus mirabilis.
  • Gene expression analysis of urease and acetogenesis in Lachnospiraceae.
  • In vivo colonization studies in mice to assess Blautia urease activity.

Main Results:

  • Urease subunits were associated with acidification in Lachnospiraceae.
  • Urease-encoding Blautia demonstrated urea-dependent changes in SCFA production, acidification, and growth.
  • Blautia directly incorporated carbon from urea into SCFAs, a trait not observed in ureolytic pathogens.
  • Co-expression of urease and acetogenesis genes was observed in healthy individuals.
  • Blautia colonization in mice reduced urea availability, confirming in vivo urease activity.
  • Acetogenic recycling of urea carbon by Blautia led to its incorporation into butyrate.

Conclusions:

  • Urea plays a central role in the physiology of health-associated Lachnospiraceae.
  • Lachnospiraceae, specifically Blautia, possess a distinct mechanism for urea utilization, differing from ureolytic pathogens.
  • This unique urea metabolism allows for carbon salvage into SCFAs and broader metabolite pools, contributing to gut health.
  • Understanding this pathway offers insights into microbial adaptation and potential therapeutic targets.