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The result of this sequential cascade is to bind ubiquitin to lysine residues on the protein substrate via an isopeptide bond, cysteine residues through a thioester bond; serine, threonine, and tyrosine residues through an ester bond; or the amino group of the protein's N-terminus via a peptide bond. [7] [8] [9] [10]
Serpins are a superfamily of proteins with similar structures that were first identified for their protease inhibition activity and are found in all kingdoms of life. [1] [2] The acronym serpin was originally coined because the first serpins to be identified act on chymotrypsin-like serine proteases (serine protease inhibitors).
The "bond" involves this linkage C−O−PO − 2 O−C. [1] Discussion of phosphodiesters is dominated by their prevalence in DNA and RNA, but phosphodiesters occur in other biomolecules, e.g. acyl carrier proteins, phospholipids and the cyclic forms of GMP and AMP (cGMP and cAMP). [2]
Phosphatidylserine (PS) is the major acidic phospholipid class that accounts for 13–15% of the phospholipids in the human cerebral cortex. [7] In the plasma membrane, PS is localized exclusively in the cytoplasmic leaflet where it forms part of protein docking sites necessary for the activation of several key signaling pathways.
Deficient expression of DNA repair proteins due to an inherited mutation can cause increased risk of cancer. Individuals with an inherited impairment in any of 34 DNA repair genes (see article DNA repair-deficiency disorder ) have an increased risk of cancer, with some defects causing up to a 100% lifetime chance of cancer (e.g. p53 mutations ...
Hydrolases can be further classified into several subclasses, based upon the bonds they act upon: EC 3.1: ester bonds (esterases: nucleases, phosphodiesterases, lipase, phosphatase) EC 3.2: sugars (DNA glycosylases, glycoside hydrolase) EC 3.3: ether bonds; EC 3.4: peptide bonds (Proteases/peptidases) EC 3.5: carbon-nitrogen bonds, other than ...
These proteins contain a conserved HSF tripeptide framework that enables a hydrophilic attack of the hydroxyl-group within the serine residue on the preceding peptide bond, converting it into an ester bond that is susceptible to cleavage by an additional nucleophile. [19] [20] [21]
Carboxylesterase 1 is a serine esterase and member of a large multigene carboxylesterase family. It is also part of the alpha/beta fold hydrolase family. [7] These enzymes are responsible for the hydrolysis of ester- and amide-bond-containing xenobiotics and drugs such as cocaine and heroin.