carboxylic acid

Examples of carboxylic acid in the following topics:

• Organic Acid Metabolism

  • The most commonly metabolized organic acids are the carboxylic acids, which are organic acids containing at least one carboxyl (-COOH) group.
  • The general formula of a carboxylic acid is R-COOH, where R is a monovalent functional group.
  • Many types of carboxylic acids can be metabolized by microbes, including:
  • Fatty acid chains are converted to enoyl-CoA (catalyzed by acyl-CoA dehydrogenase).
  • The fatty acid chain that is left over after the thiolation step can then reenter the β-oxidation pathway, which can cycle until the fatty acid has been completely reduced to acetyl-CoA.

• Vitamins and Amino Acids

  • Microorganisms and plants can synthesize many uncommon amino acids and vitamins.
  • Amino acids are biologically important organic compounds made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid.
  • About 500 amino acids are known which can be classified in many ways.
  • Microorganisms and plants can synthesize many uncommon amino acids.
  • While in plants, 1-aminocyclopropane-1-carboxylic acid is a small disubstituted cyclic amino acid that is a key intermediate in the production of the plant hormone ethylene.

• Pyruvic Acid and Metabolism

  • Pyruvic acid (CH3COCOOH) is an organic acid, a ketone, and the simplest of the alpha-keto acids.
  • Pyruvic acid (CH3COCOOH; is an organic acid, a ketone, and the simplest of the alpha-keto acids.
  • The carboxylate (COO−) anion of pyruvic acid.
  • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration); when oxygen is lacking, it ferments to produce lactic acid.
  • The cycle is also known as the citric acid cycle or tri-carboxylic acid cycle, because citric acid is one of the intermediate compounds formed during the reactions.

• Lipid Metabolism

  • Fatty acids are the building blocks of lipids.
  • They are made of a hydrocarbon chain of variable length that terminates with a carboxylic acid group (-COOH).
  • In brief, the oxidation of lipids proceeds as follows: two-carbon fragments are removed sequentially from the carboxyl end of the fatty acid after dehydrogenation, hydration, and oxidation to form a keto acid, which is then cleaved by thiolysis.
  • A fatty acid is a carboxylic acid with a long aliphatic tail that may be either saturated or unsaturated.
  • The molecule shown here is the eight-carbon saturated fatty acid known as octanoic acid (or caprylic acid).

• Aerobic Hydrocarbon Oxidation

  • Microbes can utilize hydrocarbons via a stepwise oxidation of a hydrocarbon by oxygen produces water and, successively, an alcohol, an aldehyde or a ketone, a carboxylic acid, and then a peroxide.
  • They live in the water-fuel interface of the water droplets, form dark black/brown/green, gel-like mats, and cause microbial corrosion to plastic and rubber parts of the aircraft fuel system by consuming them, and to the metal parts by the means of their acidic metabolic products.

• Siderophores

  • Siderophores are classified by which ligands they use to chelate the ferric iron, including the catecholates, hydroxamates, and carboxylates.
  • This ion state is the predominant one of iron in aqueous, non-acidic, oxygenated environments, and accumulates in common mineral phases such as iron oxides and hydroxides (the minerals that are responsible for red and yellow soil colours).
  • The majors groups of siderophores include the catecholates (phenolates), hydroxamates and carboxylates (e.g. derivatives of citric acid).
  • Citric acid can also act as a siderophore.

• The Incorporation of Nonstandard Amino Acids

  • Aside from the 22 standard amino acids, there are many other amino acids that are called non-proteinogenic or non-standard.
  • For example, the carboxylation of glutamate allows for better binding of calcium cations, and the hydroxylation of proline is critical for maintaining connective tissues.
  • Examples include lanthionine, 2-aminoisobutyric acid, dehydroalanine, and the neurotransmitter gamma-aminobutyric acid.
  • Nonstandard amino acids often occur as intermediates in the metabolic pathways for standard amino acids.
  • A rare exception to the dominance of α-amino acids in biology is the β-amino acid beta alanine (3-aminopropanoic acid), which is used in plants and microorganisms in the synthesis of pantothenic acid (vitamin B5), a component of coenzyme A.

• Amino Acid Synthesis

  • These polymers are linear and unbranched, with each amino acid within the chain attached to two neighboring amino acids.
  • Twenty-two amino acids are naturally incorporated into polypeptides and are called proteinogenic or natural amino acids.
  • Amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then transaminated to form an amino acid.
  • For example, the carboxylation of glutamate allows for better binding of calcium cations.
  • Examples include lanthionine, 2-aminoisobutyric acid, dehydroalanine, and the neurotransmitter gamma-aminobutyric acid.

• The 3-Hydroxypropionate Cycle

  • Propionyl-CoA carboxylase is an enzyme that functions in the carboxylation of propionyl CoA.
  • The acetyl-CoA carboxylase utilized in this cycle is biotin-dependent as well and catalyzes the carboxylation of acetyl-CoA to malonyl-CoA.
  • Glyoxylate, the conjugate base of glyoxylic acid, is the form that exists at a neutral pH.
  • The importance of glyoxylate within microorganisms is in its ability to convert fatty acids into carbohydrates.

• The Reverse TCA Cycle

  • The citric acid cycle (TCA) or Krebs cycle, is a process utilized by numerous organisms to generate energy via the oxidation of acetate derived from carbohydrates, fats, and proteins into carbon dioxide .
  • These enzymes are unique to reverse TCA and are necessary for the reductive carboxylation to occur.