Trypsin, chymotrypsin, cathepsin

Serine proteases usually show primary specificity (occupation of subsite Si) for positively charged arginine or lysine (trypsin, plasmin, plasminogen activators, thrombin), large hydrophobic side chains of phenylalanine, tyrosine, and tryptophan (chymotrypsin, cathepsin G, chymase, and subtilisin), or small aliphatic side chains (elastases). Nevertheless, there are a large number of variations and in many cases, other subsites like S2 and S3 are more discriminating while maintaining the... 

Hordeum vulgare (barley) (Poaceae) BSZx (44 kDa) APC, Cathepsin G Chymotrypsin Cathepsin G (L355-R356), Elastase, Factors VIIa/TF, Xa, Xlla (weak), Kallikrein, Thrombin Trypsin Cathepsin G (R356-S357) [525, 526, 532]... 

Bik inhibits the trypsin serine proteases through binding of either of its two Kunitz domains. Depending on the serine protease and the Kunitz domain involved, dissociation constants (K ) range from 0.03 to 800 pM [6, 28]. Bik fragmentation and glycation also effect strength and specificity of inhibition. For example, trypsin, chymotrypsin, kallikrein, plasmin, elastase, and cathepsin are inhibited at a A) of 0.03-3 pM, whereas Factors IXa, Xa, XIa, and Xlla are less inhibited with a A) of 15-800 pM. Protease inhibition is observed with both Kunitz domains except for Factors IXa and Xa that... 

One goal in the design of an inhibitor is specificity. Often this is a considerable challenge since physiological systems contain a number of closely related proteases. For example, there are at least four chymo-trypsin-like enzymes in humans. These include pancreatic chymotrypsin, cathepsin G, and two mast cell proteases (the human enzymes have not been characterized yet, but two are found in rats). All of these enzymes... 

Optimization of the peptide backbone of these aldehydes to take advantage of the binding interactions in the 8,-84 subsites afforded potent inhibitors of HLE, for example, aldehyde (6-6) [124]. Concurrent with the increases in potency, the selectivity of these compounds also improved. For example, aldehyde (6-5) was inactive at 100 //M against other enzymes, including the serine proteinases trypsin, chymotrypsin, and cathepsin G [125]. Aldehyde (6-5) was compared with a,-PI and was shown to be more potent in vitro (on a weight basis) and more stable towards oxidative inactivation by cigarette smoke [128]. 

None of the protein inhibitors of NE presented in this chapter are protease specific. They all inhibit more than one protease, but they are protease class specific (Table 5). For example, ai-PI, SLPI, and eglin c are serine-protease inhibitors and inhibit trypsin, chymotrypsin, and cathepsin G in addition to NE. However, ai-PI is an inhibitor of neutrophil PR3, whereas SLPI and eglin c are only very weak inhibitors of PR3 [40]. By contrast, elafin, which shares 38% homology with the C-terminal domain of SLPI, does inhibit PR3. A strong selectivity for NE is important to reduce toxicity resulting from interference of the inhibitor with other proteolytic processes. 

Interestingly, there are many such examples of proteases that exist in nature, such as, trypsin, chymotrypsin, elastase, thrombin, subtilisin, plasmin, pepsin, chymosin, cathepsin D, renin, and HIV-1 protease, etc. To illustrate the direct participation of water in the digestive mechanism we show another example of proteolysis... 

Trypsin, chymotrypsin, and cathepsin C (all from bovine), and the synthetic substrates glycyl-L-phenylalanine p-naphtylamide (GPNA), 4-phenylazo benzyloxy-car-bonyl-pro-leu-gly-pro-D-arg (PZ-peptide), N-benzoyl-L-tyrosine ethyl ester (BTEE), and Na-benzoyl-DL-arginine p-nitroanilide (BAPNA), were purchased from Sigma Chemical Co (St. Louis, MO). Fresh bluefish (Pomatomus saltatrix) and sheephead samples were purchased from a local fish market (Waldman Plus, Montreal, PQ) and kept in iCe until ready for use. 

Other syntheses were performed including one in which the action of cathepsin C and papain were coupled. It should be noted that papain exhibits stereochemical specificity toward the substrate but apparently not toward the replacing agent in these reactions. Fruton and his associates (61-63,95-97) have shown that chymotrypsin, cathepsin C, and trypsin can also catalyze transpeptidation reactions. 

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. 

Like SLPI, elafin is a very potent inhibitor of NE. Elafin interacts with elastase in a reversible manner and retains its inhibitory capacity upon dissociation of the complex. Kinetic data have shown that the association rate constant for the formation of an elafin-elastase complex is pH dependent [84]. Una is probably due to the bask properties of the inhibitor and enzyme. Elafin also inhibits proteinase 3 but has no effect on cathepsin G, trypsin, or chymotrypsin. This is inloestiitg in view of the fact that SLPI inhibits cathepsin G but la relatively ineffective against proteinase 3. 

GR 133686 (5,5-rranx-fused cyclic lactone euphane triterpene) Lantana camara (Verbenaceae) Cathepsin G (2 pM), a-Chymotrypsin (70 nM), Factor Xla (0.7 pM), Plasmin (4 pM), a-Thrombin (4 nM), Trypsin (70 nM) [112]... 

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