Serine proteases strategies

HavUr DV, Richman DD (1996) Viral dynamics of HIV implications for drug development and therapeutic strategies. Ann Intern Med 124(11) 984—994 Hinrichsen H, Benhamou Y, Wedemeyer H, Reiser M, Sentjens RE, Calleja JL, Foms X, Erhardt A, Cronlein J, Chaves RL, Yong CL, Nehmiz G, Steinmann GG (2004) Short-term antiviral efficacy of BILN 2061, a hepatitis C virus serine protease inhibitor, in hepatitis C genotype I patients. Gastroenterology 127(5) 1347-1355... 

A different strategy for measuring protease activity is based on the property of xanthene dyes to form H-type dimers (see Sect. 6.2.3) when they are in close proximity. These dimers are accompanied with a characteristic quenching of their fluorescence and, particularly for rhodamines, with a blue shift in the absorption spectrum [121, 122]. The probe D-NorFES-D designed to measure activity of elastase in HL-60 cells consists of an undecapeptide derivatized with one tetramethylrhodamine dye on each side. The sequence contains proline residues to create a bent structure and bring the two fluoro-phores in close proximity. Intact D-NorFES-D shows 90% of its fluorescence quenched plus a blue shift of the absorption spectrum. After addition of the serine protease elastase, an increase in the fluorescence and a bathochromic shift of the absorption spectrum is observed, resulting in an increase in the emission ratio [80],... 

The presence of a covalent acyl-enzyme intermediate in the catalytic reaction of the serine proteases made this class of enzymes an attractive candidate for the initial attempt at using subzero temperatures to study an enzymatic mechanism. Elastase was chosen because it is easy to crystallize, diffracts to high resolution, has an active site which is accessible to small molecules diffusing through the crystal lattice, and is stable in high concentrations of cryoprotective solvents. The strategy used in the elastase experiment was to first determine in solution the exact conditions of temperature, organic solvent, and proton activity needed to stabilize an acyl-enzyme intermediate for sufficient time for X-ray data collection, and then to prepare the complex in the preformed, cooled crystal. Solution studies were carried out in the laboratory of Professor A. L. Fink, and were summarized in Section II,A,3. Briefly, it was shown that the chromophoric substrate -carbobenzoxy-L-alanyl-/>-nitrophenyl ester would react with elastase in both solution and in crystals in 70 30 methanol-water at pH 5.2 to form a productive covalent complex. These... 

Siezen, R.J., de Vos, W.M., Lennissen, J.A.M. and Dijkstra, B.W. (1991) Homology modelling and Protein Engineering strategy of subtilases, the family of subtilisinlike serine proteases. Protein Engineering, 4, 719-737. 

This strategy was employed by Semple and co-workers [29] in the synthesis of the N(10)-C(17) fragment of cyclotheonamides, a family of 19-membered cyclic penta-peptides isolated from the sponge Theonella swinhoei, which are serine protease inhibitors. 

Factor C A Horseshoe Crab Serine Protease with Multiple High Affinity LPS-Binding Sites - LPS Detection and Prevention Strategies - Towards Non-LAL Based LPS Detection... 

The strategy used by the cysteine proteases is most similar to that used by the chymotrypsin family. In these enzymes, a cysteine residue, activated by a histidine residue, plays the role of the nucleophile that attacks the peptide bond (see Figure 9.18). in a manner quite analogous to that of the serine residue in serine proteases. An ideal example of these proteins is papain, an enzyme purified from the fruit of the papaya. Mammalian proteases homologous to papain have been discovered, most notably the cathepsins, proteins having a role in the immune and other systems. The cysteine-based active site arose independently at least twice in the course of evolution the caspases, enzymes that play a major role in apoptosis (Section 2.4.3). have active sites similar to that of papain, but their overall structures are unrelated. 

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