A Chymotrypsin

The 3-phenylpropionate ester has been used in nucleoside synthesis. It is cleaved by a-chymotrypsin (37°, 8-16 h, 70-90% yield). It can be cleaved in the presence of an acetate. ... 

A 3-phenylpropanamide, prepared from a nucleoside, is hydrolyzed under mild conditions by a-chymotrypsin (37°, pH 7, 2-12 h). ... 

Fujinaga, M., et al. Crystal and molecular structures of the complex of a-chymotrypsin with its inhibitor turkey ovomucoid third domain at 1.8 A resolution. 

Matthews, B.W., Sigler, P.B., Henderson, R., Blow, D.M. Three-dimensional structure of tosyl-a-chymotrypsin. Nature 214 652-656, 1967. 

Sigler, P.B., et al. Structure of crystalline a-chymotrypsin II. A preliminary report including a hypothesis for the activation mechanism. /. Mol. Biol. 35 143-164, 1968. 

The core protein of alphavirus has a chymotrypsin-like fold... 

Choi, H.-K., et al. Structure of Sindbis virus core protein reveals a chymotrypsin-like serine proteinase and the organization of the virion. Nature 354 37-43, 1991. 

Active a-chymotrypsin is produced from chymotrypsinogen, an inactive precursor, as shown in the color figure on page 530. 

Benzamide known as benti romide, is a chymotrypsin substrate of value as a diagnostic acid for assessment of pancreatic function. It is synthesized by amide formation between... 

The protease a-chymotrypsin has been used for transesterification reactions by two groups (Entries 7 and 8) [35, 36]. N-Acetyl-l-phenylalanine ethyl ester and N-acetyl-l-tyrosine ethyl ester were transformed into the corresponding propyl esters (Scheme 8.3-2). 

Fig. 4. HPHIC of standard proteins on the weak hydrophobic columns. The SynChro-pack PROPYL column was 25x0.41 cm Poly (alkyl aspartamid)-silicas were packed into 20 x 0.46 cm columns. Sample 25 pi containing 25 pg of each protein in buffer A. Buffer A 1.8 mol/1 ammonium sulphate + 0.1 mol/1 potassium phosphate, pH 7.0. Buffer B 0.1 mol/1 potassium phosphate, pH 7.0. Gradient 40-min linear 0-100% buffer B. Flow rate 1 ml/min. Detection A220 = 1-28 a.u.f.s. Peaks a = cytochrome C, b = ribonu-clease A, c = myoglobin, d = conalbumin, e = neochymotrypsin, / = a-chymotrypsin, g - a-chymotrypsinogen A [48]...

Chymase (mast cell protease type II), a chymotrypsin-like protease, is a serine protease found in mucosal mast cells, which catalyzes the conversion of angiotensin I to angiotensin II and of big endothelin 1 (ET1) to ET1 (1-31). 

All peptidases within a family will have a similar tertiary structure, and it is not uncommon for peptidases in one family to have a similar structure to peptidases in another family, even though there is no significant sequence similarity. Families of peptidases with similar structures and the same order of active site residues are included in the same clan. A clan name consists of two letters, the first representing the catalytic type as before, but with the extra letter P , and the second assigned sequentially. Unlike families, a clan may contain peptidases of more than one catalytic type. So far this has only been seen for peptidases with protein nucleophiles, and these clans are named with an initial P . Only three such clans are known. Clan PA includes peptidases with a chymotrypsin-like fold, which besides serine peptidases such as chymotrypsin... 

Besides this problem of designing conformationally restricted analogs for highly specific enzymes, there are Other problems to be considered in dealing with less specific enzymes. These are discussed later in the section on locked a-chymotrypsin substrates. 

Use of conformationally restricted substrate analogs for investigating the substrate specificity of a-chymotrypsin provides an instructive example of the difficulties encountered in interpreting the results of such experiments, difficulties which, as we shall see, are especially severe for relatively nonspecific enzymes. 

The conformations of the locked substrates may be only partially restricted. Indeed, this is the case for many locked substrates. Neither of the substrate analogs under consideration, for example, is restricted to only one conformation. The conformation of 25 which is active with a-chymotrypsin, however, is reasonably well known, whereas the active conformation of 24 is still controversial. 

In conclusion, one must be aware of these limitations on the use of locked substrate analogs. The problems encountered in the study of a-chymotrypsin are perhaps more severe than for most other enzymes, since a-chymotrypsin normally acts on large, polymeric substrates and is relatively nonspecific. The active site of a-chymotrypsin therefore potentially can bind small substrates such as D24 in a variety of ways. Ideally, larger conformationally restricted substrates should give more information about the active site of a-chymotrypsin. However, besides the increased problems involved in synthesizing these larger substrates, there is the problem of increased possibility of uncertainty in their conformations. 

Anand K, Palm GJ, Mesters JR, SiddeU SG, Ziebuhr J, HUgenfeld R (2002) Structure of coron-avirus main proteinase reveals combination of a chymotrypsin fold with an extra alpha-heUcal domain. EMBO J 21 3213-3224... 

The entrapment of a-chymotrypsin, lysozyme, and myehn in AOT-reversed micelles is accompanied by an increase in the micellar water content and in the size of the micelle. As a consequence of the redistribution of water among reversed micelles, the micellar solution results in being constituted by large protein-containing micelles and small unfilled ones [169],... 

The activity of a-chymotrypsin was found to be insensitive to the R value, i.e., from the size of the reversed micelles. This was taken as an indication that this enzyme is able to create its own micelles in the hydrocarbon rather than occupy empty ones and that the so-called exclusion effect, i.e., protein larger than the empty micelle cannot be solubilized, is incorrect [181,182],... 

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.

To outweigh disadvantages of the kinetic resolution presented above, an enzymatic desymmetrization of prochiral sulfinyldiacetates 19 was performed. The use of various enzymes, PLE, a-chymotrypsin (a-CT) ° and PPL," made it... 

Each enantiomer of 67 was earlier obtained by an a-chymotrypsin-catalysed resolution of its diethyl ester 68 or its cyclic analogue 69, followed by chemical hydrolysis (Scheme 6)7°... 

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