Specificity cleavage

Like all neuropeptides, NT is synthesized as part of a larger precursor that also contains neuromedin N (NN), a 6 amino acid neurotensin-like peptide (Table 1). Pro-NT/NN is processed in the regulated secretory pathway of neuroendocrine cells by prohormone convertases PCI, PC2 and PC5-A that belong to a larger family of proprotein convertases. Due to differential cleavage specificity and tissue distribution of the convertases, pro-NT/NN processing gives rise to approximately a 1 1 and a 5 1 ratio of NT over NN content in the brain and gut, respectively. The peptides are stored in secretory vesicles and released from neuroendocrine cells in a Ca2+-dependent manner. NT and NN actions are terminated by desensitization of the... 

DON T WASTE TIME ON ABSOLUTE TRIVIA UNLESS YOU HAVE THE TIME TO WASTE. It is possible to decide that something is just not worth remembering for example, cleavage specificities of proteases or restriction endonucleases, and protein molecular weights, are... 

The enzymes used for bottom-up proteomic studies can be classified as those with specific cleavage specificity and those with nonspecific proteolytic activity. 

Fig. 5.24 Classification of the phospholipases and the reaction of phospholipase C. a) Cleavage specificity of phospholipases Al, A2, C and D. b) Cleavage of inositol-containing phosphohpids by phospholipase C. In a reaction of particnlar importance for signal transduction, phosphohpase C (PL-C) catalyzes the cleavage of phosphatidyl inositol-4,5-bisphosphate (PtdIns(4,5)P2) into the messenger substances diacylglycerol and inositol 1,4,5-triphosphate (Ins(l,4,5)P3).

Phospholipase C, which occurs in different subtypes in the cell, is a key enzyme of phosphatide inositol metabohsm (for cleavage specificity, see Fig. 5.24). Two central signaling pathways regulate phosphohpase C activity of the cell in a positive way (Fig. 6.4). Phospholipases of type CP (PL-CP) are activated by G-proteins and are thus linked into signal pathways starting from G-protein-coupled receptors. Phosphohpases of type Y (PL-Cy), in contrast, are activated by transmembrane receptors with intrinsic or associated tyrosine kinase activity (see Chapter 8, Chapter 10). The nature of the extracellular stimuli activated by the two major reaction pathways is very diverse (see Fig 6.4), which is why the phosphohpase C activity of the cell is subject to multiple regulation. 

The special feature of the caspases is their high cleavage specificity. The cleavage occurs on the C terminal side of an Asp residue of the substrate protein and requires another recognition element comprised of a certain sequence of at least 3 amino acids... 

Palaniappan C, Fay PJ, Bambara RA. Nevirapine alters the cleavage specificity of ribonuclease H of human immunodeficiency virus 1 reverse transcriptase. J Biol Chem 1995 270 4861-4869. 

The cleavage specificity of trypsin is C-terminal to Lys and Arg residues (except where followed by Pro). However, not every such peptide bond will be cleaved. The number of missed cleavages to consider can be specified, but increasing the number decreases the significance of any match and should normally be set to one. 

W Sommergruber, H Ahorn, A Zophel, I Maurer-Fogy, F Fessl, G Schnorrenberg, HD Liebig, D Blaas, E Kuechler, T Skern. Cleavage specificity on synthetic peptide substrates of human rhinovirus 2 proteinase 2A. J Biol Chem 267 22639-22644, 1992. 

QM Wang, W Sommergruber, RB Johnson. Cleavage specificity of human rhinovi-rus-2 2A protease for peptide substrates. Biochem Biophys Res Commun 235 562-566, 1997. 

Figure 11. Summary of cleavage specificity of deuterolysin from A. oryzae toward calf thymus histone H14.

A. Nussbaum. From the test tube to the World Wide Web The cleavage specificity of the proteasome. PhD thesis, Eberhard-Karls-Universitaet Tuebingen, 2001. 

Proteolytic enzymes cleave specific amino acid sequences within the peptide chain of the digested protein since proteases differ in their cleavage specificities, they can have markedly different effects upon tissues depending upon the type of fixative used for processing the tissue, the antigenic target, and the epitope recognized by the antibody. 

The endopeptidases are inactivated after the digest, followed by carboxyamidomethylation of sulfhydryl groups and dimethylation of amino termini and e-amino groups of lysine residues. This forms a biologically relevant, database-searchable peptide library useful for many applications including the characterization of protease cleavage specificity. 

A particularly elegant solution for the assay of proteases and acylases is offered by the fluorogenic detection of free amino acids by decomplexation of copper from calcein, which removes its quenching effect This principle has been used for assays of acylases, amidases, and proteases (Scheme 1.13) [52, 53]. For the case of proteases combinatorial assays are particularly in demand for testing multiple peptides in parallel and determining the cleavage specificity [54]. New solutions... 

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