Inhibitors, Bowman-Birk

A different approach toward cyclic peptides has been presented by Leatherbarrow and coworkers, employing ring-dosing metathesis (RCM) on a solid support [50], The authors reported on the synthesis of conformationally strained cyclic peptides of the Bowman-Birk inhibitor type, which are naturally occurring serine protease... 

Figure 10 The global structures of Bowman-Birk inhibitors are diverse, but the reactive sites are structurally highly conserved. Reactive sites are oriented to the bottom right corner. The double-stranded /3-sheets neighboring the reactive sites are clearly visible, (a) 1 mvz, (b) 1 bbi, and (c) 1 h34. (d) The overlay of the backbone traces of the three BBIs ((a)-(c), colors as before) reveals their structural similarity. Additionally SFTI-1 (green, Ijbl) adopts the same fold in its active site. The residues (Arg in 1 mvz, Lys for other peptides) are also shown N and C denote the N- and C-termini of the truncated loops.

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... 

Krishna Murthy, H. M., et al. (1999). Crystallization, characterization and measurement of MAD data on crystals of dengue virus NS3 serine protease complexed with mung-bean Bowman-Birk inhibitor. Acta Crystallogr D 55,1370-1372. 

Murthy, H. M., et al. (2000). Crystal structure of Dengue virus NS3 protease in complex with a Bowman-Birk inhibitor implications for flaviviral polyprotein processing and drug design. /. Mol. Biol. 301, 759-767. 

Baturay. N. Kennedy, A.R. (1986) Pyrene acts as a cocarcinogen with the carcinogens benzo[o]pyrene, P-propiolactone and radiation in the induction of malignant transformation in cultured mouse fibroblasts soybean extract containing the Bowman-Birk inhibitor acts as an anticarcinogen. Cell Biol. Toxicol., 2, 21-32... 

Among the EST database of ragi sequences, there are two groups of bifunctional proteinase inhibitor trypsin a-amylase from seeds of ragi sequences. The upper clade was further subdivided (Fig. 6.10). Wang et al. (2008) concluded that there was great diversity in the sequence of different Bowman-Birk inhibitors in emmer wheat both within and between populations. 

FIGURE 6.10 Divergences in sequence of some ragi EST clones from that of an authentic Bowman Birk inhibitor (gi 94959241) using the Maximum Composite Likelihood Pairwise distance calculation and Mega4 (Tamura et al., 2007). 

Chymotrypsin (3.4.21.1) Avazyme, Chyrnar, Enzeon, Quimar Calcium (3-Phenylpropionate [26], aprotinin [5,44,45,141-144], Bowman-Birk inhibitor [7,141,145], benzyloxycarbonyl-Pro-Phe-CHO [43], chicken ovoinhibitor [47], chymostatin [3,141], DFP [26], FK-448 [3], PMSF [26], polycarbophil-cysteine [67], soybean trypsin inhibitor [5,7,51], sugar biphenylboronic acids complexes [146], poly(acrylate) derivatives [49]... 

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],... 

Poly(acrylic acid)-Bowman-Birk inhibitor conjugate [59], poly(acrylic acid)-chymostatin conjugate [172]... 

Birk, Y. 1985. The Bowman-Birk inhibitor. Int J Pept Protein Res 25 113. 

Chymotrypsin Aprotinin, benzyloxycarbonyl-Pro-Phe-CHO, Bowman-Birk inhibitor, chicken ovoinhibitor, chymostatin, 4-(4-isopropyl piperadinocarbonyl)phenyl 1,2,3,4-tetrahydro-l-naphthoate methanesulphonate, soybean trypsin inhibitor... 

In cells tested, the Bowman-Birk inhibitor is more potent than the Kunitz inhibitor in decreasing cell growth. Thus, it appears that the antichymotrypsin activity is modulating growth of these cells. 

The Bowman-Birk type protease inhibitors represent a class of low molecular weight, cysteine-rich proteins found in legume seeds (.10). The major Bowman-Birk inhibitor in soybean seeds is a double-headed protein capable of blocking the activity of both trypsin and chymotrypsin. This protein represents approximately 4% of the total protein in soybean seeds (1J ). In contrast to the soybean trypsin inhibitor (Kunitz), the "double-headed inhibitor (referred to as BB) is typical of protease inhibitors present in a large number of legume seeds for example, peanuts (12) chick peas (33)5 kidney beans (3JO adzuki beans (33) lima beans (16). 

The Bowman-Birk inhibitor also blocks the transformation of C H/10T1/2 cells (18). This raises the speculation that BB may represent a direct acting nutritionally relevant anticarcinogen particularly in the case of colon cancer. In this regard it was recently reported that e-aminocaproic acid (a trypsin inhibitor) inhibits dimethylhydrazine-induced colon tumors in mice (22). 

Does the active form of the Bowman-Birk inhibitor reach the colon If so, what is the effect on colon tumor cells ... 

Isolation, iodination and metabolic studies with 125I-BB The Bowman-Birk inhibitor was isolated as previously described (11 ). For metabolic studies BB was iodinated and purified using chymotrypsin-sepharose (18). C-H/HEN mice were administered I-BB by gavage and sacrificed after one hour. 

Polypeptides Aprotinin (Kimura et al. 1996, Saffran et al. 1988, Yamamoto et al. 1994), Bowman-Birk inhibitor, Kunitz trypsin inhibitor, chicken egg white trypsin inhibitor (Reseland et al. 1996, Ushirogawa 1992), chicken ovoinhibitor (Scott et al. 1987), human pancreatic trypsin... 

Trypsin/chymotrypsin Bowman-Birk inhibitor from Lens culinaris L. culinaris... 

SFTI-1 is a 14 amino acid cyclic peptide expressed in the seeds of sunflowers.91 As its name suggests, it is a potent trypsin inhibitor, and indeed is the most potent Bowman-Birk inhibitor (BBI) known, with a subnanomolar inhibition constant for trypsin. Although not strictly a toxin, since its natural function is not yet known, we include it here because of our focus on cyclic peptides from plants, and because other trypsin inhibitors from plants are regarded as toxins because of their toxic effects on insect pests. 

---