Kunitz

Table 17.1 Phage-optimized sequences of Kunitz domain libraries primary binding loop...

How do the mutations identified by phage display improve binding specificity There is as yet no direct stmctural information on the phage-selected inhibitors however they can be modeled using data from the crystal structures of other Kunitz domains bound to serine proteinases. These studies lead to the conclusion that the mutations identified by phage display improve binding specificity by maximizing complementarity between the... 

Dennis, M.S., Herzka, A., Lazarus, R.A. Potent and selective Kunitz domain inhibitors of plasma kallikrein designed by phage display. /. Biol. Chem. 270 25411-25417, 1995. 

Some of the best investigated anti-nutrients are the enzyme inhibitors present in legumes and other plants. The Bowman-Birk and the Kunitz inhibitors of trypsin and other proteases are among the best characterized. In contrast to the non-specific and widespread influences of tannins and lectins (Carmona, 1996), the Bowman-Birk, Kunitz and other such inhibitors target specific enzymes. Corresponding with this, proteases and other digestive enzymes vary in sensitivity to the different inhibitors. 

Tissue factor pathway inhibitor (TFPI), a 42-kDa protein with three Kunitz domains, is a potent inhibitor of coagulation. It inhibits tissue factor-factor Vila complex upon binding to the active site of Kunitz domain one. Factor Xa is inhibited upon binding to the active site of the second Kunitz domain of TFPI (27). 

Fig. 6. Mechanism of inhibition of tissue factor pathway inhibitor (TFPI). Kunitz domain 1 (Dl) inhibits TF-VIIa complex. Domain 2 (D2) inhibits Xa.

Bozas, S.E., Panaccio, M., Creaney, J., Dosen, M., Parsons, J.C., Vlasuk, G.V., Walker, I.D. and Spithill, T.W. (1995) Characterisation of a novel Kunitz-type molecule from the trematode Fasciola hepatica. Molecular and Biochemical Parasitology 74, 19-29. 

Honisberger, M., and Tacchini-Vonlanthen, M. (1983) Ultrastructural localization of Kunitz inhibitor on thin sections of Glycine max (soybean) cv. Maple Arrow by the gold method. Histochemistry 77, 37-50. 

JOFUKU, K.D., SCHIPPER, R.D., GOLDBERG, R.B., A ffameshift mutation prevents Kunitz trypsin-inhibitor messenger-RNA accumulation in soybean embryos, Plant Cell, 1989,1,427-435. 

KU BPTI/Kunitz family of serine protease inhibitors E(M) 0(0) 42(141) 1AAL... 

Northrop, J.H., Kunitz, M., Herriott, R.M. (1939). Crystalline Enzymes. Columbia University Press, New York. 

Itil TM, Eralp E, Ahmed I, Kunitz A, Itil KZ. (1998). The pharmacological effects of ginkgo biloba, a plant extract, on the brain of dementia patients in comparison with tacrine. Psychopharmacol Bull. 34(3) 391-97. 

Based on their sequence homology, disulfide connectivity, and cysteine location within the sequence and chemistry of the reactive site. Pis can be assigned to distinct families, as classified by Laskowski and Kato. Kunitz-type, Bowman—Birk-type, Potato type I and type II, and squash inhibitors are members of these families shown in Table 3. For inhibitors not falling into these classifications more families have been proposed. Pis can also be classified by their target/mode of action. Plants have been found to express Pis that target serine proteinases, cysteine proteinases, aspartic proteinases, and metallo-proteinases. Serine and cysteine protease inhibitors are the best-studied PIs. ... 

Kunitz-type protease inhibitors usually are large polypeptides of more than 120 amino acids and will not be discussed here, based on the focus of the review being peptides of fewer than 100 amino acids in length. Searches of publicly available databases yield a few short sequences, which are fragments from larger proteins that have only been partially sequenced. 

I Soybean trypsin inhibitor (Kunitz-type) PF00197... 

Figure 13.8. Solubility curves of chymotiypsinogen A in two different solvents. Adapted from J. H. Northrop, M. Kunitz, and R. M. Heiriot, Crystalline Enzymes, 2nd ed., Columbia University Press, New York, 1948. Originally published in J. Gen. Physiol. 24, 196 (1940) reproduced by copyright permission of the Rockefeller University Press.

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