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(S,S)-(+)-Ethambutol is powerful and selective antitubercular drug.It is a typical example of an old drug that was introduced for clinical use in its unichiral form. . Ethambutol contains two constitutionally symmetrical chiral centers in its structure and exists in three stereoisomeric forms, the enantiomeric pair (+)-(S,S)- and (−)-(R,R)-ethambutol, along with the achiral stereoisomer called m
An achiral environment does not differentiate the molecular twins whereas a chiral environment does distinguish the left-handed version from the right-handed version. Human body, a classic bio-environment, is inherently handed as it is filled with chiral discriminators like amino acids, enzymes, carbohydrates, lipids, nucleic acids, etc.
The non-reducing sugar then acts as a glycosyl acceptor as a protecting group that is easily lost in solution reveals a free hydroxyl group. This reacts with a donor that was disarmed, forming the oxocarbenium ion at a slower rate, producing the desired trisaccharide.
An enantiopure drug is a pharmaceutical that is available in one specific enantiomeric form. Most biological molecules (proteins, sugars, etc.) are present in only one of many chiral forms, so different enantiomers of a chiral drug molecule bind differently (or not at all) to target receptors .
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Mannoheptulose is a competitive and non-competitive inhibitor of both hexokinase and the related liver isozyme glucokinase. [2] [3] [4] By blocking the enzyme hexokinase, it prevents glucose phosphorylation, the first step in the fundamental biochemical pathway of glycolysis. As a result, the breakdown of glucose is inhibited.
Glycosylation also plays a role in cell-to-cell adhesion (a mechanism employed by cells of the immune system) via sugar-binding proteins called lectins, which recognize specific carbohydrate moieties. [2] Glycosylation is an important parameter in the optimization of many glycoprotein-based drugs such as monoclonal antibodies. [6]
In enzymology, an alternansucrase (EC 2.4.1.140) is an enzyme that catalyzes a chemical reaction that transfers an alpha-D-glucosyl residue from sucrose alternately to the 6- and 3-positions of the non-reducing terminal residue of an alpha-D-glucan, thereby creating a glucan with alternating alpha-1,6- and alpha-1,3-bonds.