Legumes protease inhibitor

Faba beans contain several ANFs such as tannins, protease inhibitors (vicin/ convicin) and lectins. Use of low-vicin/convicin cultivars may allow substantial levels of faba beans to be included in poultry diets (Danner, 2003). The levels of trypsin inhibitor and lectin activities are low compared with other legume seeds and do not pose problems in poultry diets when faba beans are incorporated into diets at the levels shown below. Of most concern for poultry is the tannin fraction, which has been shown to depress digestibility of the protein and AA (Ortiz et al., 1993). Tannins in whole faba beans are associated with the seedcoat (testa), and the tannin content is related to the colour of the seedcoat (and flowers). Tannins are lower in white than in the colour-seeded varieties. 

In common with many other legume seeds, raw lentils contain some undesirable constituents, although the levels of these are not likely to be of concern in poultry feeding. Weder (1981) reported the presence of several protease inhibitors in lentils. Marquardt and Bell (1988) also identified lectins (hemagglutinins), phytic acid, saponins and tannins as potential problems but could find no evidence that these had adversely affected performance of pigs fed lentils. It is known that cooking improves the nutritive value of lentils for humans but the effects of consumption of raw lentils by non-ruminants have not been well documented (Castell, 1990). 

Weder, J.K.P. (1981) Protease inhibitors in the leguminosae. In Pothill, R.M. and Raven, PH. (eds) Advances in Legume Systematic s. British Museum of Natural History, London, pp. 533-560. 

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). 

Legumes are able to fix atmospheric nitrogen via symbiotic Rhizobia in root nodules. Thus, nitrogen is easily available for secondary metabolism, and it is probably not surprising that nitrogen-containing SM (alkaloids, nonprotein amino acids [NPAAs], cyanogens, protease inhibitors, lectins) are a common theme in... 

Table 8. Bowman-Birk serine protease inhibitors from legumes...

Legume (Fabaceae) Bowman-Birk protease inhibitor proteins (BBPIPs) are typically double-headed protease inhibitors with 14 cysteines (i.e. 7 S-S links) and molecular masses of 7-9 kDa. All the BBPIPs listed were isolated from seeds except for the Medicago sativa (alfalfa) leaf BBPIPs. For other details see the legend to Table 4. 

Various non-legume, non-Poaceae Bowman-Birk protease inhibitors have been isolated that have sequence homology to the other BBPIPs [137-140, 285-288] (Table 10). The Ananas BBPIPs are disulphide-linked heterodimers [137-140]. The Helianthus BBPIP SFTI-1 is a small cyclic peptide (cyclotide) [285, 286] whereas the Solanum tuberosum BBPIP is similar to the single-headed Poaceae BBPIPs [287, 288]. 

Table 10. Non-legume, non-cereal Bowman-Birk protease inhibitor homologues...

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