Search results
Results from the WOW.Com Content Network
Cysteine (/ ˈ s ɪ s t ɪ iː n /; [5] symbol Cys or C [6]) is a semiessential [7] proteinogenic amino acid with the formula HOOC−CH(−NH 2)−CH 2 −SH. The thiol side chain in cysteine enables the formation of disulfide bonds, and often participates in enzymatic reactions as a nucleophile. Cysteine is chiral, but both D and L-cysteine ...
As the functional group of the amino acid cysteine, the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can generate a cystine unit with a disulfide bond (−S−S−).
In computational biology, protein pK a calculations are used to estimate the pK a values of amino acids as they exist within proteins.These calculations complement the pK a values reported for amino acids in their free state, and are used frequently within the fields of molecular modeling, structural bioinformatics, and computational biology.
The reducing power of DTT is limited to pH values above 7, since only the negatively charged thiolate form -S − is reactive (the protonated thiol form -SH is not); the pKa of the thiol groups is 9.2 and 10.1. Reduction of a typical disulfide bond by DTT via two sequential thiol-disulfide exchange reactions.
The most commonly used nucleophiles are the hydroxyl (OH) of serine and the thiol/thiolate ion (SH/S −) of cysteine. [2] Alternatively, threonine proteases use the secondary hydroxyl of threonine, however due to steric hindrance of the side chain's extra methyl group , such proteases use their N -terminal amide as the base rather than a ...
Cysteine proteases are commonly encountered in fruits including the papaya, pineapple, fig and kiwifruit. The proportion of protease tends to be higher when the fruit is unripe. In fact, the latex of dozens of different plant families are known to contain cysteine proteases. [2] Cysteine proteases are used as an ingredient in meat tenderizers.
It is commonly used to bind covalently with the thiol group of cysteine so the protein cannot form disulfide bonds. [2] [3] It is also used in ubiquitin studies as an inhibitor of deubiquitinase enzymes (DUBs) because it alkylates the cysteine residues at the DUB active site.
Reaction with thiols occur in the pH range 6.5–7.5, NEM may react with amines or undergo hydrolysis at a more alkaline pH. NEM has been widely used to probe the functional role of thiol groups in enzymology. NEM is an irreversible inhibitor of all cysteine peptidases, with alkylation occurring at the active site thiol group (see schematic ...