Egg white trypsin inhibitor

Further inhibitors of this class are the chicken egg white trypsin inhibitor (= chicken ovomucoid 186 amino acids) [46], the chicken ovoinhibitor (449 amino acids) [47], and the human pancreatic trypsin inhibitor (56 amino acids), which can already be produced in Escherichia coli [48]. 

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... 

Fraenkel-Conrat H, Bean RS, Lineweaver H. Essential groups for the interaction of ovomucoid (egg white trypsin inhibitor) and trypsin, and for tryptic activity. J. Biol. Chem. 1949 177 385-403. 

H. Fraenkel-Conrat, R. S. Bean and H.Lineweaver, Essential Groups for the Interaction of Ovomucoid (Egg White Trypsin Inhibitor) and Trypsin, and for Tryptic Activity, J. biol. Chem. 177, 385 03 (1949). 

About 20 families of protein inhibitors of proteases have been described.488 The egg white ovomucoids comprise one family. Turkey ovomucoid is a three-domain protein whose 56-residue third domain is a potent inhibitor of most serine proteases.455 489 The 58-residue pancreatic trypsin inhibitor490 is a member of another family of small proteins. A 36-residue insect (locust) protease inhibitor is even smaller.491... 

Enzyme inhibitors of a protein nature are of significant concern because of widespread occurrence. The most common of these affect the pancreatic enzymes, trypsin and chymotrypsin. and arc found in legumes, as well as in egg whites and potatoes. 

Figure B3.1.3 An isoelectric focusing (IEF) gel, pH 3 to 10. Lane 1, 4 pg purified egg white cystatin. Lane M, broad-range pi standards trypsinogen (pi 9.3), lentil lectin-basic band (pi 8.65), lentil lectin-middle band (pi 8.45), lentil lectin-acidic band (pi 8.15), myoglobin-basic band (pi 7.35 visible as a broad band), myoglobin-acidic band (pi 6.85), human carbonic anhydrase B (pi 6.55), bovine carbonic anhydrase (pi 5.85), a-lactoglobulin A (pi 5.20), soybean trypsin inhibitor (pi 4.55), and amyloglucosidase (pi 3.50) in order shown from top of gel. The pi values of the two purified egg white cystatin isomers were determined to be 6.6 (upper band) and 5.8 (lower band). Adapted from Akpinar (1998) with permission from author.

Figure B3.1.4 A 15% SDS-pdyacrylamide gel assayed for proteinase inhibitors. (A) Gel stained with Coomassie brilliant blue for total protein. (B) Gel assayed for serine-proteinase inhibitory activity against trypsin. Food-grade proteinase inhibitors used in surimi manufacture were assayed. Lane 1, whey protein concentrate. Lane 2, bovine plasma proteins. Lane 3, egg white. Each lane contains 15 pg protein. Lane M, molecular weight standards. The dark bands in (B) indicate proteins with proteinase inhibitory activity. Numerous proteins in egg white (lane 3) are shown to have inhibitory activity against trypsin. Adapted from Weerasinghe (1995).

There are examples of inhibitors which are specific for only one protease within a group. The best known examples Include the Kunitz soybean (Glycine max) inhibitor (14) and isoinhibitors I and II of the Great Northern bean (Phaseolus vulgaris)(15). Even these two examples are not clear cut as there is some small non-stoichiometric combination and inhibition of a-chymotrypsin. Chicken (16) and Japanese quail (17) egg white ovomucoids only inhibit trypsin. 

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) ... 

H.Lineweaver and C.W. Murray, Identification of the Trypsin Inhibitor of Egg White with Ovomucoid, J. biol. Chem. 171, 565-581 (1947). 

Figure 21 Dependences of In k on the reciprocal of the logarithm of the organic solvent concentration ln(1 /Dq] (where ln(1 /Dq] = 0 for several proteins eluted from an r -octylsihca sorbent under RPC conditions using a 50% formic acid mobiie phase and 2-propanol as the organic soivent modifier at a flow rate of 1.0mL/min. The legend for the proteins 1, hen egg ovalbumin 2, bovine pancreatic trypsin inhibitor 3. hen egg white iysozyme 4, horse heart cytochrome c 5, bovine insuiin 6, bovine giucagon and 7, tovine pancreatic ribonudease. (Data from Ref. 154.)...

Lineweaver, H., and Murray, C. W. (1947). Identification of the trypsin Inhibitor of egg white with ovomucoid. J. Biol. 

Physical characterization of ovoinhibitor, a trypsin and chyraotrypsin inhibitor from chicken egg white. Arch. 

Of the large number of known proteinase inhibitors, only those corr5>ounds found in foods are of interest in food chemistry. These include in particular the inhibitors in egg white, plant seeds, and plant nodules. Table 16.12 shows the most important sources of proteinase inhibitors, which have molecular weights between 6000 and 50,000. The specificity for proteinases varies considerably. Some inhibitors inhibit only trypsin, many act on both tiypsin and ch)motrypsin, and others inhibit microbial or plant proteinases as well, e. g., subtilisin or papain. Proteinase inhibitors are often located in. 

Inhibitor activity is normally determined with commercial animal enzymes, e. g., bovine trypsin or bovine chymotrypsin. The evaluation of a potential effect of the inhibitors on human health assumes that the inhibition of human enzymes is known. Present data show that inhibitors from legumes generally inhibit human trypsin to the same extent or a little less than bovine trypsin. On the other hand, human chymotrypsin is inhibited to a much greater extent by most legumes. Ovomucoid and ovoinhibitor from egg white as well as the Kazal inhibitor from bovine pancreas do not inhibit the human enzymes. The Kunitz inhibitor from bovine pancreas inhibits human trypsin but not chymotrypsin. The data obtained greatly depend not only on the substrate used, but also on the enzyme preparation and the reaction conditions, e. g., on the ratio enzyme/inhibitor. The stability of an inhibitor as it passes through the stomach must also be taken into account in the evaluation of a potential effect (cf. Table 16.15). The Kunitz inhibitor of soybeans, for... 

Native ovoflavoprotein (49 kDa, pf=5.1) has, as does ovomucoid, certain antinutritional effects, as it inhibits serine proteases (trypsin, chymotrypsin and also microbial proteases) and has antiviral activity. Ovomacroglobulin (ovostatin) is an inhibitor of serine, cysteine, thiol and metalloproteases and shows antimicrobial activity. Some antinutritional effects are also seen in the basic glycoprotein avidin in raw egg white (relative molecular weight of the monomer is 15.6 kDa). It contains four identical subunits (pf = 9.5), each of which binds one molecule of biotin to give an unavailable complex. However, the denatured avidin, for example in hard-boiled eggs, does not interact with biotin. The interaction of riboflavin with flavoprotein (32 kDa, pf = 4.0) has, on the contrary, a positive influence on vitamin stability. Cystatin acts as cysteine protease inhibitor, and shows antimicrobial, antitumor and immunomodulating activities. 

Heating can also have favorable effects. Heating soybean flour improves the utilization of protein by making the amino acid methionine more available, and heating raw soybeans destroys the inhibitor of the protein digestive enzyme trypsin. Cooking eggs destroys the trypsin inhibitor ovomucoid in the white. 

Figure 7 Correlation between predicted and experimental pK s in nine globular proteins hen egg white lysozyme, ribonuclease A, turkey ovomucid third domain, bovine pancreatic trypsin inhibitor, B1 and B2 immuno obulin G binding domains of protein G, a-chymotrypsin, ribonuclease Tj, lysozyme T4, and staphylococcal nuclease.

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