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Threonine (symbol Thr or T) [2] is an amino acid that is used in the biosynthesis of proteins.It contains an α-amino group (which is in the protonated −NH + 3 form when dissolved in water), a carboxyl group (which is in the deprotonated −COO − form when dissolved in water), and a side chain containing a hydroxyl group, making it a polar, uncharged amino acid.
Threonine proteases use the secondary alcohol of their N-terminal threonine as a nucleophile to perform catalysis. [1] [2] The threonine must be N-terminal since the terminal amine of the same residue acts as a general base by polarising an ordered water which deprotonates the alcohol to increase its reactivity as a nucleophile.
In addition to the common amino acid L-tyrosine, which is the para isomer (para-tyr, p-tyr or 4-hydroxyphenylalanine), there are two additional regioisomers, namely meta-tyrosine (also known as 3-hydroxyphenylalanine, L-m-tyrosine, and m-tyr) and ortho-tyrosine (o-tyr or 2-hydroxyphenylalanine), that occur in nature.
Allothreonine is an amino acid with the formula CH 3 CH(OH)CH(NH 2)CO 2 H. It is the diastereomer of the amino acid threonine. Like most other amino acids, allothreonine is a water-soluble colorless solid. Although not one of the proteinogenic amino acids, it has often been the subject for the synthesis of novel proteins using an expanded ...
Threonine proteases use the amino acid threonine as their catalytic nucleophile. Unlike cysteine and serine, threonine is a secondary hydroxyl (i.e. has a methyl group). This methyl group greatly restricts the possible orientations of triad and substrate as the methyl clashes with either the enzyme backbone or histidine base. [2]
Used in proteins and as a storage for ammonia, it is the most abundant amino acid in the body. Arginine: R Arg Functionally similar to lysine. Serine: S Ser Serine and threonine have a short group ended with a hydroxyl group. Its hydrogen is easy to remove, so serine and threonine often act as hydrogen donors in enzymes.
The acid-base properties of the imidazole side chain are relevant to the catalytic mechanism of many enzymes. [10] In catalytic triads, the basic nitrogen of histidine abstracts a proton from serine, threonine, or cysteine to activate it as a nucleophile. In a histidine proton shuttle, histidine is used to quickly shuttle protons. It can do ...
Asn-Gly (NG),is the most flexible and since it is acidic, it is most prone to deamidation with a half-life around 24 h under physiological conditions (pH 7.4, 37 °C). [3] As a free amino acid, or as the N-terminal residue of a peptide or protein, glutamine deamidates readily to form pyroglutamic acid (5-oxoproline). The reaction proceeds via ...