Proteolysis Chymotrypsin

Stavridi, E. S., O Malley, K., Lukacs, C. M., et al., 1996. Structural change in o -chymotrypsin induced by complexation widi o l-antitrypsin as. seen by enhanced. sen.sitivity to proteolysis. Biochemistry 35 10608-10615. 

Figure 9-6. Selective proteolysis and associated conformational changes form the active site of chymotrypsin, which includes the Aspl 02-His57-Ser195 catalytic triad. Successive proteolysis forms prochymotrypsin (pro-CT), Jt-chymotrypsin (jt-CT),and ultimately a-chymotrypsin (a-CT), an active protease whose three peptides remain associated by covalent inter-chain disulfide bonds.

Selected entries from Methods in Enzymology [vol, page(s)] Sulfonylation reaction, 11, 706 reaction kinetics, 11, 707 second-order rate constants for inactivation of chymotrypsin, trypsin, and acetylcholine esterase by PMSE and related sulfonylat-ing agents, 11, 707 reactivation of PMS-chymotrypsin, 11, 710 as inhibitor [of calcium-activated factor, 80, 674 of cathepsin G, 80, 565 of crayfish trypsin, 80, 639 of elastase, 80, 587 of pro-lylcarboxypeptidase, 80, 465 of protease Re, 80, 691 of protease So, 80, 695 of protein C, 80, 329] proteolysis, 76, 7. 

A method for analyzing protein structure based on limited proteolysis. This method is especially useful in investigations of membrane proteins whose membrane association limits the repertoire of techniques that can be gainfully applied to infer structural features. For example, Davis et al used four proteases to assess the topology of yeast H -ATPase reconstituted into phosphatidyl-serine vesicles. Limited proteolysis by trypsin and a-chymotrypsin inactivates the enzyme and produces stable, membrane-bound fragments. Sequence analyses of... 

Proteolysis of peptides and proteins by enzymes occurs in a selective or nonselective manner. Chymotrypsin, trypsin, lysyl endopeptidase, Staphylococcus aureus V8 protease, and en-dopeptidase Asp-N are frequently listed as selective enzymes, whereas thermolysin, pepsin, subtilisin, and elastase belong to the nonselective enzymes, although thermolysin preferentially cleaves peptide bonds before hydrophobic residues. 

Resistance of inhibitors to gut proteolysis has been improved by various methods such as replacement of phenylalanine at P3 with O-methyl tyrosine (or naphthylalanine), which was shown to abolish chymotrypsin cleavage and yet retain high inhibitory potency for renin [40]. 

Some of the serine proteases are stored in the pancreas as inactive precursors that may be activated by proteolysis. Trypsinogen, for example, is converted to trypsin by the removal of the N-terminal hexapeptide on the cleavage of the bond between Lys-6 and Ile-7 by enterokinase. Chymotrypsinogen is activated by the tryptic cleavage of the bond between Arg-15 and He-16. (In this case, further proteolysis by the chymotrypsin that is released during the activation leads to the different forms of the enzyme—Figure 16.5.)... 

Limited proteolysis by thermolysin, papain, subtilsin and a-chymotrypsin of the plasma-membrane-bound adenylate cyclase from rat liver had no effect on activity when Mn2+ was the cofactor, but stimulated activity in the presence of Mg2+. However, the addition of Mg2+ over MnATP did not result in stimulation on proteolysis. The simplest interpretation is that proteolysis exerts its main effect on the regulatory components of adenylate cyclase.329 Adenylate cyclase, solubilized from rat liver membranes by Lubrol PX or deoxycholate, loses its regulatory components, and becomes much more specific for MnATP.330... 

Horikoshi, T., Igarashi, S., Uchiwa, H., Brysk, H., and Brysk, M.M. Role of endogenous cathepsin D-like and chymotrypsin-like proteolysis in human epidermal desquamation, Br. J. Dermatol., 141, 453-9, 1999. 

Drags that structurally resemble nutrients such as polypeptides, nucleotides, or fatty acids may be especially susceptible to enzymatic degradation. For example, the proteolytic enzymes chymotrypsin and trypsin can degrade insulin and other peptide drags. In the case of insulin, proteolysis was shown to be reduced by the coadmmistration of carbopol polymers at 1% and 4% (w/v%), which presumably shifted the intestinal pH away from the optimal pH for proteolytic degradation. 

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