Chymotrypsin inhibitor

Fig. 5. Protein folding. The unfolded polypeptide chain coUapses and assembles to form simple stmctural motifs such as -sheets and a-hehces by nucleation-condensation mechanisms involving the formation of hydrogen bonds and van der Waal s interactions. Small proteins (eg, chymotrypsin inhibitor 2) attain their final (tertiary) stmcture in this way. Larger proteins and multiple protein assembhes aggregate by recognition and docking of multiple domains (eg, -barrels, a-helix bundles), often displaying positive cooperativity. Many noncovalent interactions, including hydrogen bonding, van der Waal s and electrostatic interactions, and the hydrophobic effect are exploited to create the final, compact protein assembly. Further stmctural...

Protein inhibitors are often active against a variety of en2ymes, although each molecule may possess a separate and very distinct binding site for each en2yme. For example, many trypsin and chymotrypsin inhibitors are identical compounds (12). 

Lupine seed, though used primarily in animal feeds (see Feeds AND FEED ADDITIVES), does have potential for use in human appHcations as a replacement for soy flour, and is reported to contain both trypsin inhibitors and hemagglutenins (17). The former are heat labile at 90°C for 8 minutes the latter seem much more stable to normal cooking temperatures. Various tropical root crops, including yam, cassava, and taro, are also known to contain both trypsin and chymotrypsin inhibitors, and certain varieties of sweet potatoes may also be impHcated (18). 

CARVALHO M R, SGARBiERi V 0 (1998) Relative importance of phytohemagglutinin (lectin) and trypsin-chymotrypsin inhibitor on bean (Phaseolus vulgaris L) protein absorption and utilization by the rat. JNutr Sci Vitaminol (Tokyo). 44 685-96. 

Figure 7.11 Linear free energy correlation plots for inhibition of subtilisin BPN mutants by wild type (open circles) and mutant (close circles) chymotrypsin inhibitor 2. Left panel Correlation between AGbinding for the inhibitor and AGm. Right panel Correlation between AGbinding for the inhibitor and AGES.

Pan, Y. P. Daggett, V., Direct comparison of experimental and calculated folding free energies for hydrophobic deletion mutants of chymotrypsin inhibitor. 2 Free energy perturbation calculations using transition and denatured states from molecular dynamics simulations of unfolding, Biochemistry 2001,40, 2723-2731. 

A large number of potential reversible protease inhibitors exist (Laskowski Kato, 1980). Protein protease inhibitors like Strepromyces Subtilisin Inhibitor (SSI) (Hiromi et al, 1985) and Chymotrypsin Inhibitor (CI-2) (Jonassen, 1980 and McPhalen James, 1988) are known to be very strong inhibitors with inhibition constants at or below 10"10 M. 

Li A. and Daggett V. Identification and characterization of the unfolding transition state of chymotrypsin inhibitor 2 by molecular dynamics simulations. J. Mol. Biol. 

X.-Y. Liu, K. O. Cottrell, and T. M. Nordlund, Spectroscopy and fluorescence quenching of tyrosine in lima bean trypsin/chymotrypsin inhibitor and model peptides, Photochem. 

Cyanobacteria -Microcystis aeruginosa Micropeptins 478-A and -B -peptide-based plasmin inhibitors Cyanopeptolins A-D -protease inhibitors Cyanopeptolin 963A-chymotrypsin inhibitor 120 6, 262 263... 

Potl inhibitors differ from other protease inhibitors, and from all other defense peptides mentioned thus far, in their relative lack of disulfide bonds. This means that the loop with the reactive site is not fixed, as it is in the Bowman-Birk inhibitors, yet they still form a stable fold, as shown in Figure 11. An interesting feature of some Potl inhibitors is their tendency to form stable, noncovalently bound oligomers. This has, for example, been shown for chymotrypsin inhibitor I from tomato. This peptide has a monomer weight of 8300 Da under dissociating sodium dodecyl sulfate (SDS) gel conditions. Gel filtration and ultracentrifugal analysis revealed a... 

Despite their lack of stabilizing disulfide bridges Potl inhibitors feature a common, stable fold. The N-terminus is coiled, although in some structures a small /3-strand has been identified. After a turn the structure adopts an a-helical structure, followed by a turn and an other /3-strand. The sequence then features an extended turn or loop motif that contains the reactive site of the inhibitor before it proceeds with a /3-strand running almost parallel to the /3-strand after the a-helix. After another turn and coiled motif a short /3-strand antiparallel to the other /3-strands precedes the coiled C-terminus. Usually the N-terminal residue in the reactive site is an acidic residue followed by an aromatic amino acid, that is, tyrosine or phenylalanine. Figure 11 shows the complex of chymotrypsin inhibitor (Cl) 2 with subtilisin, the hexamer of Cl 2 from H. vulgare and a structural comparison with a trypsin inhibitor from Linum usitatissimum ... 

Fujii, S., Yokoyama, T., Ikegaya, K., Sato, F., and Yokoo, N. (1985). Promoting effect of the new chymotrypsin inhibitor Fk-448 on the intestinal absorption of insulin in rats and dogs. J. Pharm. Pharmacol., 37, 545-549. 

Fiqure 17.2 Denaturation of wild-type and two destabilized mutants of chymotrypsin inhibitor 2 (CI2) induced by gnanidinium chloride. Substituting equation 17.6 into equation 17.5 gives... 

Chymotrypsinogen 480, 481 Chymotrypsin inhibitor 2 (CI2) folding kinetics 544-577, 577 GroEL binding 605 fragments 577, 578, 587, 588, 595 mechanism of folding 576-588 structure 576, 577 Circular dichroism (CD) 193-195 optimal absorbance for signal to noise 212-214... 

Another cultivation of Microcystis aeruginosa NIVA Cya 43 yielded the new cyanopeptolin 954 (1004), which is a chymotrypsin inhibitor (1041). The newly isolated chlorodysinosin A (1005), from a Dysidea sponge, has been synthesized and its structure confirmed (1042). 

Shivraj, B., Rao, H. N., and Pattiraman, T. N. (1982). Natural plant inhibitors. Isolation of a trypsin/a-amylase inhibitor and a chymotrypsin inhibitor from ragi (Eleusine coracana) grains by affinity chromatography and study of their properties. J. Sci. Food Agric. 33,1080-1091. 

The Bowman-Birk soybean trypsin and chymotrypsin inhibitor modulates the growth of human colon and breast cancer cells. 

K. Hatanc, M. Kqjima, M. Tanokura, and K, Takahaihi. Solution structure of bromelain inhibitor VI from pineapple stem structural similarity with Bawmnn-Birk hyprin/chymotrypsin inhibitor from soybean. Biochemistry J5 5379 (1996). 

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