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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 are a family of proteolytic enzymes harbouring a threonine (Thr) residue within the active site. The prototype members of this class of enzymes are the catalytic subunits of the proteasome , however, the acyltransferases convergently evolved the same active site geometry and mechanism .
In enzymology, a threonine-tRNA ligase (EC 6.1.1.3) is an enzyme that catalyzes the chemical reaction. ATP + L-threonine + tRNA(Thr) AMP + diphosphate + L-threonyl-tRNA(Thr) The three substrates of this enzyme are ATP, L-threonine, and threonine-specific transfer RNA [tRNA(Thr)], whereas its three products are AMP, diphosphate, and L-threonyl-tRNA(Thr).
O-GlcNAcylation and phosphorylation can occur on the same threonine and serine residues, suggesting a complex relationship between these modifications that can affect many functions of the cell. [6] [12] The modification affects processes like the cells response to cellular stress, the cell cycle, protein stability and protein turnover.
Many serine/threonine protein kinases do not have their own individual EC numbers and use 2.7.11.1, "non-specific serine/threonine protein kinase". This entry is for any enzyme that phosphorylates proteins while converting ATP to ADP (i.e., ATP:protein phosphotransferases.) [10] 2.7.11.37 "protein kinase" was the former generic placeholder and was split into several entries (including 2.7.11.1 ...
ATM serine/threonine kinase or Ataxia-telangiectasia mutated, symbol ATM, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks (canonical pathway), oxidative stress, topoisomerase cleavage complexes, splicing intermediates, R-loops and in some cases by single-strand DNA breaks. [5]
Protein kinases and phosphatases work independently and in a balance to regulate the function of proteins. [3] The amino acids most commonly phosphorylated are serine, threonine, tyrosine, and histidine. [4] [5] These phosphorylations play important and well-characterized roles in signaling pathways and metabolism.
Threonine ammonia-lyase (EC 4.3.1.19, systematic name L-threonine ammonia-lyase (2-oxobutanoate-forming), also commonly referred to as threonine deaminase or threonine dehydratase, is an enzyme responsible for catalyzing the conversion of L-threonine into α-ketobutyrate and ammonia: