Kunitz domains inhibitors

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. 

Dennis, M S. and Lazarus, R. A. (1994) Kunitz domain inhibitors of tissue factor-factor Vila II Potent and specific inhibitors by competitive phage selection J. Biol. Chem. 269, 22,137—22,144. 

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... 

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.

Enjyoji K, Miyaya X Kamikubo Y Kato H, Effect of heparin on the inhibition of factor Xa by tissue factor pathway inhibitor a segment, Gly 212-Phe 243, of the third Kunitz domain is a heparin binding site. Biochemistry 1995 34 5725-5735,... 

Xu Y, Carr PD, Guss JM, Ollis DL. The crystal structure of bikunin from the inter-a-inhibitor complex A serine protease inhibitor with two kunitz domains. J Mol Biol 1998 276 955-966. 

If thrombin and factor Xa, the major activated blood coagulation factors (Fig. 11.6), escape into healthy blood vessels, blood clots will develop and occlude capillaries throughout the body. Direct inhibition of these activated enzymes in the blood flow utilizes serine protease inhibitors, of which there are two common types a Kunitz inhibitor and a serpin. The former possess a Kunitz domain, a convex antiparallel (1-sheet that exactly fits into the concave active site of a serine protease, directly blocking it (lock and key mechanism). By contrast, serpins undergo complex interactions with other proteins to cause conformational changes that bait and block the catalytic action (Fig. 11.12 shows the bait). Table 11.3 fists the major coagulation inhibitors and cofactors, their targets and mechanisms of action. 

Tissue factor pathway inhibitor (TFPI) is a Kunitz type inhibitor composed of three Kunitz domains. The N-terminal Kunitz domain binds to and inhibits the VHa-TF complex that activates factor X (Fig. 11.6a), whereas the downstream Kunitz domain binds directly to factor Xa and inhibits it strongly and permanently. No function has yet been demonstrated for the third Kunitz domain. The C-terminal region of TFPI is basic and remains attached to endothelial cell surfaces where it inhibits inadvertent factor Xa activation. Studies in mice indicate that knocking out the gene for TFPI stops fetal development. Indeed, clotting diseases such as a stroke and heart attacks are associated with mutations of AITH, HCII and ZPI, but not of TFPI. Like TF (Sect. 11.3.1), diminished TFPI activity may be incompatible with life. 

There appears to be sequence homology between the pineapple stem bromelain inhibitors and some of the small molecular weight inhibitors from the legumlnosae (91) Human inter-a-trypsin inhibitor contains two domains with great similarity to the domains of the Kunitz-type inhibitors (44 92-94)> The ovoinhibitors from Japanese quail and chicken egg whites contain six tandem domains which are homologous to the Kazal pancreatic secretory inhibitor and to the ovomucoids (69) ... 

It has been known for some time that many examples of naturally occurring Kunitz inhibitors exist, both isolated and as domains in larger proteins, which inhibit a variety of serine proteases [47]. This strongly suggests that this molecular framework is compatible with inhibition of this general class. The contact region between these inhibitors and their protease targets is known from a... 

Protease nexin 2 is identical to the secreted form of the amyloid precursor protein containing the Kunitz-type serine protease inhibitor domain (128,129), Protease nexin 2 circulates in blood stored as a platelet a-granule protein, which is secreted upon platelet activation (127). Protease nexin 2 inhibits trypsin- and chymotrypsin-like serine proteases and is also a potent inhibitor of factor Xla (126,127,128). Its location in platelets and its ability to inhibit factor Xla suggests a role in regulating blood coagulation for protease nexin 2. 

Girard TJ, Warren LA, Novotny Wp Likert KM, Brown SG, Miletich JR et al. Functional significance of the Kunitz-type inhibitory domains of lipoprotein-associated coagulation inhibitor. Nature 1989 338 518-520. 

Three proteins, for which I did not have structural data, should also be mentioned, namely the so-called minibody [147-149] a Kunitz inhibitor domain of the human lipoprotein associated coagulation inhibitor (LACI-D1 Refs. 89 and 90) which resembles BPTI and CP-1, a designed scaffold zinc-finger [150], The minibody is a 61 aa designed... 

Bikunin (Bik), a peptide excreted in the urine, is one of the primary inhibitors of the trypsin family of serine proteases. This peptide plays a key role in inflammation and innate immunity because of its two Kunitz-type binding domains [1, 2], Bik suppresses proteolytic activity in a variety of tissues and can also exert localized anti-inflammatory effect [3-5], Inflammation is an important indicator of infection, cancer, and tissue injury in acute and chronic states. In acute inflammation, fluids and plasma components accumulate in the affected tissues due to vascular dilation. Subsequent activation of platelets and increased presence of immune cells occur during repair. Long-standing inflammation may be present before the disorder is identified. Due to its inhibitory role and potential use as an early marker of inflammation, we will review the synthesis, structure, pathophysiology of Bik as well as the various approaches for its measurement in this chapter. 

Morishita H, Yamakawa T, Matsusue T, Kusuyama T, Sameshima-Aruga R, Hirose J, et al. Novel factor Xa and plasma kallikrein inhibitory activities of the second Kunitz-type inhibitory domain of urinary trypsin inhibitor. Thromb Res 1994 73 193-204. 

APP transcripts have been identified in which exons 7, 8, and 15 are alternatively spliced. Exon 7 encodes 57 amino acids with homology to the Kunitz-type protease inhibitor (KPI) domain (Kitaguchi et al., 1988 Ponte et al., 1988 Tanzi et al., 1988) and exon 8 (Kitaguchi et al., 1988 Lemaire et al., 1989). The A3 peptide is encoded by parts of both exons 16 and 17 (exon and codon numbering based on the APP770 splice variant) (Lemaire et al., 1989) (Pig. 2). In neurons, the predominant isoform is APP695 (Weidemann et al., 1989), which contains exon 15 but excludes exons... 

Although pancreatic secretory trypsin inhibitor (Kazal inhibitor) has not been studied by DSC to our knowledge, it is included because it is homologous to the domains of ovomucoids and ovoinhibi-tors (Laskowski and Kato, 1980). Both the porcine and bovine Kazal inhibitors are relatively stable (Menegatti et al., 1981 De Marco et al., 1982), but less so than the Kunitz inhibitor (BPTI). 

Inhibitors of Bowman-Birk types are widely distributed in plants and significantly different from the Kunitz inhibitor in their amino acid composition and are able to interact not only with trypsin, but with chymotrypsin (Valueva Mosolov, 2002 Rawlings et al., 2004). Inhibitors of Bowman-Birk type characterized by the presence of two reactive centers on a single polypeptide chain rich in cysteine (7 or more residues in one polypeptide), and the lack of amino acid residues tryptophan and tyrosine. The molecular weight of such inhibitors can vary from 8 to 16 kDa. Sometimes there are inhibitors that contain two domains on one polypeptide chain and active only in relation to one type of enzyme (Valueva Mosolov, 2002 Yan et al., 2009 Mosolov Valueva, 2008). 

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