Search results
Results from the WOW.Com Content Network
Homocysteine thiolactone (HTL) is an organosulfur compound with the formula H 2 NCHC(O)SCH 2 CH 2. It is the thiolactone (intramolecular thioester ) of homocysteine . It is produced by methionyl-tRNA synthetase in an error-editing reaction that prevents translational incorporation of homocysteine into proteins .
Homocysteine can cyclize to give homocysteine thiolactone, a five-membered heterocycle. Because of this "self-looping" reaction, homocysteine-containing peptides tend to cleave themselves by reactions generating oxidative stress. [12] Homocysteine also acts as an allosteric antagonist at Dopamine D 2 receptors. [13]
The activation of the drug clopidogrel (top left) gives a thiolactone, which ring-opens. [3] Thiolactones are intermediates in the activation of some drugs. [4] In nature, the most common thiolactone is homocysteine thiolactone. It is produced from homocysteine. It may play a role in protein damage. [5]
The production of homocysteine through transsulfuration allows the conversion of this intermediate to methionine, through a methylation reaction carried out by methionine synthase. The reverse pathway is present in several organisms, including humans, and involves the transfer of the thiol group from homocysteine to cysteine via a similar ...
Protons tunnel across a series of hydrogen bonds between hydronium ions and water molecules.. The Grotthuss mechanism (also known as proton jumping) is a model for the process by which an 'excess' proton or proton defect diffuses through the hydrogen bond network of water molecules or other hydrogen-bonded liquids through the formation and concomitant cleavage of covalent bonds involving ...
Transmethylation is a biologically important organic chemical reaction in which a methyl group is transferred from one compound to another. An example of transmethylation is the recovery of methionine from homocysteine. In order to sustain sufficient reaction rates during metabolic stress, this reaction requires adequate levels of vitamin B 12 ...
Examples of molecules that follow this process are potassium K +, sodium Na +, and calcium Ca 2+. A place in the human body where this occurs is in the intestines with the uptake of glucose . Secondary active transport is when one solute moves down the electrochemical gradient to produce enough energy to force the transport of another solute ...
Homocysteine (left) and methionine (right) are related by demethylation and remethylation. Remethylation is a major step in the conversion of homocysteine to the essential amino acid methionine . The remethylation process involves the enzyme methionine synthase (MS), which requires vitamin B 12 as a cofactor, and also depends indirectly on ...