Glucoronic acid (from Ancient Greek"sweet" + "urine") is a carboxylic acid. Itsstructure is similar to that of glucose. However, glucuronic acids sixth carbon is oxidized to a carboxylic acid. Its formula is C6H10O7. The salts and esters of glucuronic acid are known as glucuronates;the anion C6H9O7− is the glucuronate ion. Glucuronic acid should not be confused with gluconic acid, a linear carboxylic acidresulting from the oxidation of a different carbon of glucose. Both glucuronic acid andgluconic acid are reported to be found in the fermented drink known as kombucha. IUPAC name (2S,3S,4S,5R,6R)-3,4,5,6-Tetrahydroxyoxane-2-carboxylic acidBy Norbert Hoffmann:Glucuronic acid is considered by many to be one of the important key components found inKombucha Tea because of its detoxifying action. It is widely distributed in plants, found ingums, mucilages, saponines etc. and in animals. The related compound, UDPGlucuronicacid which is the active or co-enzyme form of Glucuronic acid, has been discovered inseveral non-Kombucha bacteria by at least eight scientists (Dutton, 1980). Since metabolicprocesses in related organisms are generally similar, it can, therefore, be expected thatUDP-Glucuronic acid is also present in the Kombucha bacteria. This, of course, still has tobe substantiated. It is this compound which binds toxins in the body and allows theirelimination. Dutton (1966) states that "the biosynthesis of the simple conjugates ofGlucuronic acid was shown to occur, somewhat ironically, ... by glucuronyl transference froman active form, UDP (uridinediphosphate)-Glucuronic acid, and (it was) demonstrated thatthis nucleotide was derived, in animals, not from glucuronate, but from glucose by way ofUDP-glucose
Uronic acid pathway (Glucuronic acid cycle) :1- The Glc-6-P is converted into Glc-1-P that takes high energy UTPand becomes UDP-Glc by the enzyme UDP-Glc dehydrogenase(NAD+ is required).
2- UDP gluclucuronic acid is produced and conjugated withGlucosamine and Galactosamine to form mucopolysaccharides.Utilized in detoxification by conjugation with Benzene (phenol),Bilirubin and other steroids.3- UDP-glucuronic acid loses UMP and becomes D-glucuronic acid 1-P less, then loses Pi(phosphate) to become D-glucuronic acid,which may also come from diet (like meat) and this convert to L-glucuronic acid byreductase.4- L-glucuronic acid is either converted into:a- L-gulonolactone which is converted into 2 keto L-gulonolactonethat results in ascorbic acid (vit. C)this step is absent in human, primates (Monkeys) and guineapigs, because of enzyme absence, So no vit. C is formed. But inother animals the enzyme’s present and thus vit. C can besunthesized.b- L-Xylulose is formed by decarboxylation and then reduced byNADPH to L-xylitol (alcohol) which loses H+ to NAD to becomeNADH and D-Xylulose results by a reductase enzyme, so if thisenzyme is deficient then L-Xylulose accumulates in the blood,causing “Essential Pentoseuria”.D-Xylulose converts to Xylulose 5-P by kinase and by HMP shuntRibose-5-P is produced then Frc-6-P and Glyceraldehyde-3-Pare formed and so pyruvic acid that’s oxidized to CO2, H2O andenergy is produced
Proteoglycans: Glucuronic acid is common in carbohydrate chains of proteoglycans. It is part ofmucous animal secretions (such as saliva), cell glycocalyx andintercellular matrix (forinstance hyaluronan)Glucuronidases: Glucuronidases are those enzymes that hydrolyze the glycosidic bond betweenglucuronic acid and some other compound.Glucuronidation: In the animal body, glucuronic acid is often linked to the xenobiotic metabolism ofSubstances such as drugs,pollutants, bilirubin, androgens,estrogens, mineralocorticoids, glucocorticoids, fattyacid derivatives, retinoids, and bile acids. These linkages involve glycosidic bonds, and thislinkage process is known as glucuronidation. Glucuronidation occurs mainly in the liver,although the enzyme responsible for its catalysis, UDP-glucuronyltransferase, has beenfound in all major body organs, e.g., intestine, kidneys, brain, adrenal gland, spleen,and thymus.
Glucuronidation in the Cat: The cat can glucuronidate bilirubin but cannot glucuronidate phenolic compoundssuch as phenol and napthol.Glucuronides: The substances resulting from glucuronidation are known as glucuronides (orglucuronosides) and are typically much more water soluble than the non-glucuronic acid-containing substance from which they were originally synthesised. The human body usesglucuronidation to make a large variety of substances more water-soluble, and, in this way,allow for their subsequent elimination from the body through urine or faeces (via bile from theliver). Hormones may also be glucuronidated to allow for easier transport around the body.Pharmacologists have linked drugs to glucuronic acid to allow for more effective delivery of abroad range of substances. Sometimes toxic substances are also less toxic afterglucuronidation,The conjugation of xenobiotic molecules with hydrophilic molecular species such asglucuronic acid is known as phase II metabolism The β-D methyl glycoside of glucuronic acid in the low energy 4C1 conformationUDP-Glucuronic Acid Functions:UDP-Glucuronic acid has three major functions: Detoxification of poisonous substances through conjugation and subsequent elimination.
Transport of hormones and other important substances through conjugation and subsequent release at the target location, tissue etc. . Intermediate in the biosynthesis of Ascorbic acid (except in primates and guinea pigs).The Detoxification Process UDP-Glucuronic acid is formed in the liver of all animals including primates andconjugates (combines with) poisonous substances making them more water-soluble to allowfor subsequent elimination. This binding of poisonous compounds is catalyzed by theenzyme UDP-Glucuronyltransferase which has been found in all major body organs, heart,kidneys, adrenal gland, spleen, thymus etc. Another enzyme, Glucuronidase, works the opposite way. It can break the conjugated substances (glucuronides) apart again to free hormones and other chemicals where they are needed. It is controlled by a substance called Saccharolactone which can inhibit its action. In addition, naturally occurring bacteria in the intestines use this enzyme to break down some of the glucuronides into its components, allowing reabsorption of Glucuronic acid and the conjugated substance (toxin or drug) provided it is lipid soluble, through the intestinal walls. This explains why certain drugs normally excreted with feces remain in the body longer than anticipated, for example glutethimide (Doriden) and phenolpthalein. Toxins with smaller molecules normally are excreted with urine thus escaping biotransformation by bacterial enzymes.
Uses: Determination of urinary steroids and of steroid conjugates in blood Contained in somecommercially available brands of Kombucha as an antioxidant & organic acid In all plantsand mammals-other than guinea pigs and primates-glucuronic acid is a precursor of ascorbic acid, also known as vitamin c.