Metabolism is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks of proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transportation of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism.
Isoleucine (symbol Ile or I) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH+3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a hydrocarbon side chain with a branch (a central carbon atom bound to three other carbon atoms). It is classified as a non-polar, uncharged (at physiological pH), branched-chain, aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it. Essential amino acids are necessary in the human diet. In plants isoleucine can be synthesized from threonine and methionine. In plants and bacteria, isoleucine is synthesized from pyruvate employing leucine biosynthesis enzymes. It is encoded by the codons AUU, AUC, and AUA.
Threonine is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, a carboxyl group, and a side chain containing a hydroxyl group, making it a polar, uncharged amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Threonine is synthesized from aspartate in bacteria such as E. coli. It is encoded by all the codons starting AC.
Valine (symbol Val or V) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isopropyl group, making it a non-polar aliphatic amino acid. Valine is essential in humans, meaning the body cannot synthesize it; it must be obtained from dietary sources which are foods that contain proteins, such as meats, dairy products, soy products, beans and legumes. It is encoded by all codons starting with GU (GUU, GUC, GUA, and GUG).
Butyric acid, also known under the systematic name butanoic acid, is a straight-chain alkyl carboxylic acid with the chemical formula CH3CH2CH2CO2H. It is an oily, colorless liquid with an unpleasant odor. Isobutyric acid is an isomer. Salts and esters of butyric acid are known as butyrates or butanoates. The acid does not occur widely in nature, but its esters are widespread. It is a common industrial chemical and an important component in the mammalian gut.
Propionic acid is a naturally occurring carboxylic acid with chemical formula CH
3CH
2CO
2H. It is a liquid with a pungent and unpleasant smell somewhat resembling body odor. The anion CH
3CH
2CO−
2 as well as the salts and esters of propionic acid are known as propionates or propanoates.
Dehydroalanine is a dehydroamino acid. It does not exist in its free form, but it occurs naturally as a residue found in peptides of microbial origin. As an amino acid residue, it is unusual because it has an unsaturated backbone.
Ceramides are a family of waxy lipid molecules. A ceramide is composed of sphingosine and a fatty acid joined by an amide bond. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells, since they are component lipids that make up sphingomyelin, one of the major lipids in the lipid bilayer. Contrary to previous assumptions that ceramides and other sphingolipids found in cell membrane were purely supporting structural elements, ceramide can participate in a variety of cellular signaling: examples include regulating differentiation, proliferation, and programmed cell death (PCD) of cells.
Gut microbiota, gut microbiome, or gut flora are the microorganisms, including bacteria, archaea, fungi, and viruses, that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut microbiota. The gut is the main location of the human microbiome. The gut microbiota has broad impacts, including effects on colonization, resistance to pathogens, maintaining the intestinal epithelium, metabolizing dietary and pharmaceutical compounds, controlling immune function, and even behavior through the gut–brain axis.
Histidine ammonia-lyase is an enzyme that in humans is encoded by the HAL gene. It converts histidine into ammonia and urocanic acid. Its systematic name is L-histidine ammonia-lyase (urocanate-forming).
Formiminoglutamic acid is an intermediate in the catabolism of L-histidine to L-glutamic acid. It thus is also a biomarker for intracellular levels of folate. The FIGLU test is used to identify vitamin B₁₂ deficiency, folate deficiency, and liver failure or liver disease. It is elevated with folate trapping, where it is accompanied by decreased methylmalonic acid, increased folate and a decrease in homocysteine.
Short-chain fatty acids (SCFAs) are fatty acids of two to six carbon atoms. The SCFAs' lower limit is interpreted differently, either with one, two, three or four carbon atoms. Derived from intestinal microbial fermentation of indigestible foods, SCFAs in human gut are acetic, propionic and butyric acid. They are the main energy source of colonocytes, making them crucial to gastrointestinal health. SCFAs all possess varying degrees of water solubility, which distinguishes them from longer chain fatty acids that are immiscible.
Free fatty acid receptors (FFARs) are G-protein coupled receptors (GPRs). GPRs are a large family of receptors. They reside on their parent cells' surface membranes, bind any one of a specific set of ligands that they recognize, and thereby are activated to elicit certain types of responses in their parent cells. Humans express more than 800 different types of GPCRs. FFARs are GPCR that bind and thereby become activated by particular fatty acids. In general, these binding/activating fatty acids are straight-chain fatty acids consisting of a carboxylic acid residue, i.e., -COOH, attached to aliphatic chains, i.e. carbon atom chains of varying lengths with each carbon being bound to 1, 2 or 3 hydrogens. For example, propionic acid is a short-chain fatty acid consisting of 3 carbons (C's), CH3-CH2-COOH, and docosahexaenoic acid is a very long-chain polyunsaturated fatty acid consisting of 22 C's and six double bonds : CH3-CH2-CH1=CH1-CH2-CH1=CH1-CH2-CH1=CH1-CH2-CH1=CH1-CH2-CH1=CH1-CH2-CH1=CH1-CH2-CH2-COOH.
The enzyme phenylalanine ammonia lyase (EC 4.3.1.24) catalyzes the conversion of L-phenylalanine to ammonia and trans-cinnamic acid.:
Free fatty acid receptor 1 (FFAR1), also known as G-protein coupled receptor 40 (GPR40), is a rhodopsin-like G-protein coupled receptor that is coded by the FFAR1 gene. This gene is located on the short arm of chromosome 19 at position 13.12. G protein-coupled receptors reside on their parent cells' surface membranes, bind any one of the specific set of ligands that they recognize, and thereby are activated to trigger certain responses in their parent cells. FFAR1 is a member of a small family of structurally and functionally related GPRs termed free fatty acid receptors (FFARs). This family includes at least three other FFARs viz., FFAR2, FFAR3, and FFAR4. FFARs bind and thereby are activated by certain fatty acids.
Free fatty acid receptor 3 protein is a G protein coupled receptor that in humans is encoded by the FFAR3 gene. GPRs reside on cell surfaces, bind specific signaling molecules, and thereby are activated to trigger certain functional responses in their parent cells. FFAR3 is a member of the free fatty acid receptor group of GPRs that includes FFAR1, FFAR2, and FFAR4. All of these FFARs are activated by fatty acids. FFAR3 and FFAR2 are activated by certain short-chain fatty acids (SC-FAs), i.e., fatty acids consisting of 2 to 6 carbon atoms whereas FFFAR1 and FFAR4 are activated by certain fatty acids that are 6 to more than 21 carbon atoms long. Hydroxycarboxylic acid receptor 2 is also activated by a SC-FA that activate FFAR3, i.e., butyric acid.
Free fatty acid receptor 2 (FFAR2), also termed G-protein coupled receptor 43 (GPR43), is a rhodopsin-like G-protein coupled receptor. It is coded by the FFAR2 gene. In humans, the FFAR2 gene is located on the long arm of chromosome 19 at position 13.12. Like other GPCRs, FFAR2s reside on the surface membrane of cells and when bond to one of their activating ligands regulate the function of their parent cells. FFAR2 is a member of a small family of structurally and functionally related GPRs termed free fatty acid receptors (FFARs). This family includes three other receptors which, like FFAR2, are activated by certain fatty acids: FFAR1, FFAR3 (GPR41), and FFAR4 (GPR120). FFAR2 and FFAR3 are activated by short-chain fatty acids whereas FFAR1 and FFAR4 are activated by long-chain fatty acids.
Free Fatty acid receptor 4 (FFAR4), also termed G-protein coupled receptor 120 (GPR120), is a protein that in humans is encoded by the FFAR4 gene. This gene is located on the long arm of chromosome 10 at position 23.33. G protein-coupled receptors reside on their parent cells' surface membranes, bind any one of the specific set of ligands that they recognize, and thereby are activated to trigger certain responses in their parent cells. FFAR4 is a rhodopsin-like GPR in the broad family of GPRs which in humans are encoded by more than 800 different genes. It is also a member of a small family of structurally and functionally related GPRs that include at least three other free fatty acid receptors (FFARs) viz., FFAR1, FFAR2, and FFAR3. These four FFARs bind and thereby are activated by certain fatty acids.
Imidazolidinones are a class of 5-membered ring heterocycles structurally related to imidazolidine. Imidazolidinones feature a saturated C3N2 nucleus, except for the presence of a urea or amide functional group in the 2 or 4 positions.
Imidazolinones or imidazolones are a family of heterocyclic compounds, the parents of which have the formula OC(NH)2(CH)2. Two isomers are possible, depending on the location of the carbonyl (CO) group. The NH groups are nonadjacent. A common route to imidazol-2-ones involves condensation of ureas and acyloins. Some are of interest in the pharmaceuticals. 4-Imidazolones arise from the condensation of amidines with 1,2-dicarbonyls such as glyoxal.
