Carboxypeptidase Chymotrypsin

Chymotrypsin, 170,171, 172, 173 Classical partition functions, 42,44,77 Classical trajectories, 78, 81 Cobalt, as cofactor for carboxypeptidase A, 204-205. See also Enzyme cofactors Condensed-phase reactions, 42-46, 215 Configuration interaction treatment, 14,30 Conformational analysis, 111-117,209 Conjugated gradient methods, 115-116. See also Energy minimization methods Consistent force field approach, 113 Coulomb integrals, 16, 27 Coulomb interactions, in macromolecules, 109, 123-126... 

There are two main classes of proteolytic digestive enzymes (proteases), with different specificities for the amino acids forming the peptide bond to be hydrolyzed. Endopeptidases hydrolyze peptide bonds between specific amino acids throughout the molecule. They are the first enzymes to act, yielding a larger number of smaller fragments, eg, pepsin in the gastric juice and trypsin, chymotrypsin, and elastase secreted into the small intestine by the pancreas. Exopeptidases catalyze the hydrolysis of peptide bonds, one at a time, fi"om the ends of polypeptides. Carboxypeptidases, secreted in the pancreatic juice, release amino acids from rhe free carboxyl terminal, and aminopeptidases, secreted by the intestinal mucosal cells, release amino acids from the amino terminal. Dipeptides, which are not substrates for exopeptidases, are hydrolyzed in the brush border of intestinal mucosal cells by dipeptidases. 

The effects of various enzymes on the activity of HPLC fractions that inhibited 3H-PCP binding were investigated. As shown in table 1, pronase (0.5 pg/ml), carboxypeptidase A (0.1 unit/ml), and trypsin (3.0 g/ml ) markedly decreased the potency of 10 n units of PCP-like activity. No significant change in activity was. seen when fractions were incubated with alpha-chymotrypsin. 

Some of the pancreatic enzymes in the lumen include pancreatic amylase, pancreatic lipase, elastase, trypsin, a-chymotrypsin, and carboxypeptidase A. For example, the aspirin derivatives aspirin phenylalanine ethyl ester, aspirin phenyllactic ethyl ester, and aspirin phenylalanine amide have been studied as substrates for carboxypeptidase A [67,68], with the phenylalanine ethyl ester derivative proving to be the best substrate. This study indicated that the carboxypeptidase A may serve as a reconversion site for many drug derivatives. 

Peptides Trypsin chymotrypsin carboxypeptidase Hydrolyze peptides into di- and tripeptides Pancreas Small intestine... 

Indeed, all three peptides were rather rapidly degraded by rat jejunal homogenates with tm values of 12-32 min. The peptides 6.84 and 6.85 were also hydrolyzed in rat and human jejunal fluid, whereas 6.86 was less sensitive [211], When examined in the presence of purified enzymes, the three peptides showed different reactivities. The peptides 6.84 and 6.85 were very rapidly degraded by chymotrypsin (f1/2 ca. 1 min) and rapidly by trypsin (tm ca. 20 min) [212], Hydrolysis by carboxypeptidase A was almost as fast as... 

Trypsin, chymotrypsin, elastase, etc. Subtilisin Papain, actinidin Thermolysin Carboxypeptidase Acid proteases Isomerases... 

Chemical reactivity and hydrogen bonding 320 Proton-transfer behaviour 321 Intramolecular hydrogen-bond catalysis 344 Enzyme catalysis and hydrogen bonding 354 Chymotrypsin 354 Thermolysin 355 Carboxypeptidase 355 Tyrosyl tRNA synthetase 356 Summary 366 Acknowledgements 367 References 367... 

A novel concept of using bioadhesive polymers as enzyme inhibitors has been developed [97]. Included are derivatives of poly acrylic acid, polycarbophil, and car-bomer to protect therapeutically important proteins and peptides from proteolytic activity of enzymes, endopeptidases (trypsin and a-chymotrypsin), exopeptidases (carboxypeptidases A and B), and microsomal and cytosolic leucine aminopeptidase. However, cysteine protease (pyroglutamyl aminopeptidase) is not inhibited by polycarbophil and carbomer [97]. 

Numerous peptides have been prepared starting from trifluoromethylalanine. 31, 120 Cyclopeptides containing a-trifluoromethyl amino acids have also be prepared. Some peptidic coupling performed with other a-trifluoromethyl amino acids involve protease catalysis (subtilisin, a-chymotrypsin, carboxypeptidase Y, trypsin, etc.). ... 

Thiosulfate cyanide sulfurtransferase symmetry in 78 TTiiouridine 234 Three-dimensional structures of aconitase 689 adenylate kinase 655 aldehyde oxido-reductase 891 D-amino acid oxidase 791 a-amylase, pancreatic 607 aspartate aminotransferase 57,135 catalytic intermediates 752 aspartate carbamyltransferase 348 aspartate chemoreceptor 562 bacteriophage P22 66 cadherin 408 calmodulin 317 carbonic acid anhydrase I 679 carboxypeptidase A 64 catalase 853 cholera toxin 333, 546 chymotrypsin 611 citrate synthase 702, 703 cutinase 134 cyclosporin 488 cytochrome c 847 cytochrome c peroxidase 849 dihydrofolate reductase 807 DNA 214, 223,228,229, 241 DNA complex... 

In the acylation step a nucleophilic group on one of the amino-acid side chains at the active site behaves as the nucleophile. As we have seen in Section 25-9B, the nucleophile of carboxypeptidase is the free carboxyl group of glutamic acid 270. In several other enzymes (chymotrypsin, subtilisin, trypsin, elastase, thrombin, acetylcholinesterase), it is the hydroxyl group of a serine residue ... 

You may have wondered how the proteolytic enzymes such as trypsin, pepsin, chymotrypsin, carboxypeptidase, and others keep from self-destructing by catalyzing their own hydrolysis or by hydrolyzing each other. An interesting feature of the digestive enzymes is that they are produced in an inactive form in the stomach or the pancreas—presumably to protect the different kinds of proteolytic enzymes from attacking each other or other proteins. 

Fig. 14. The rate of hydrolysis of RNase relative to that of Ox-RNase as a function of temperature. The proteases used were (O) aminopeptidase, (A) trypsin, ( ) chymotrypsin, and ( ) carboxypeptidase. Reproduced from Klee (.340).

Trypsin, chymotrypsin, and elastase—three members of the serine protease family—catalyze the hydrolysis of proteins at internal peptide bonds adjacent to different types of amino acids. Trypsin prefers lysine or arginine residues chymotrypsin, aromatic side chains and elastase, small, nonpolar residues. Carboxypeptidases A and B, which are not serine proteases, cut the peptide bond at the carboxyl-terminal end of the chain. Carboxypeptidase A preferentially removes aromatic residues carboxypeptidase B, basic residues. (Illustration copyright by Irving Geis. Reprinted by permission.)... 

Trypsin, chymotrypsin, carboxypeptidase A and B, elastase, pepsin, phospholipase... 

Hypertensin is soluble in alcohol, glacial acetic acid, phenol, and water, and insoluble in ether (61). Because it is inactivated by tyrosinase it probably contains a catechol or phenol group, and by amine oxidase, an amine group on an a-carbon atom (Figure 2). Hypertensin is inactivated by certain phenolic, catecholic, and amine oxidases, by pepsin, trypsin, chymotrypsin, and carboxypeptidase, and by hypertensinase found in plasma. The nature of hypertensinase is unknown, but it is probably not an oxidative enzyme. Because it is heat-labile, hypertensinase can be removed from blood and renin preparations by heating hypertensin itself is heat-stable. Lack of pure preparations of hypertensin has delayed its further chemical identification. 

Aprotinin is a polypeptide consisting of 58 amino acid residues derived from bovine lung tissues and shows inhibitory activity toward various proteolytic enzymes including chymo-trypsin, kallikrein, plasmin, and trypsin. It was also one of the first enzyme inhibitors used as an auxiliary agent for oral (poly)peptide administration. The co-administration of aprotinin led to an increased bioavailability of peptide and protein drugs [5,44,45], The Bowman-Birk inhibitor (71 amino acids, 8 kDa) and the Kunitz trypsin inhibitor (184 amino acids, 21 kDa) belong to the soybean trypsin inhibitors. Both are known to inhibit trypsin, chymotrypsin, and elastase, whereas carboxypeptidase A and B cannot be inhibited [7,46],... 

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