Protease Inhibitors of Plant Origin and Role of Protease Inhibitors in Human Nutrition Overview
Protein protease inhibitors are widely distributed among different botanical families in the plant kingdom (reviewed by Liener and Kakade, 1980). Their common source is the seed but they are also present in tubers and leaves. Most of them are proteins with M r values in the range of 8000–10,000 but there are a few notable exceptions. The inhibitors differ in specificities, most of them inhibit trypsin and many inhibit chymotrypsin. They are frequently multiheaded as a consequence of gene elongation via gene multiplication. Different kinds of inhibitors can be present in a single tissue as exemplified in barley grains, soybeans, and potato tubers (reviewed by Birk, 1987). Their presence in valuable plant foods and their possible involvement in nutritive and physiological properties have attracted the attention of nutritionists. The nutritional significance of protease inhibitors in foods has recently been discussed (Friedman, 1986). The physiological significance of plant protease inhibitors in situ has been questioned for a long time. The hypothesis that the inhibitors may have evolved as a defense mechanism of plants toward insects has been supported by various studies (reviewed by Birk, 1987). The extensively studied inhibitors of serine proteases have been classified into inhibitor families on the basis of sequence homology, assignment of the inhibitory site(s), and interaction with the protease(s) according to a standard mechanism (Laskowski and Kato, 1980; Laskowski, 1986). Since the inhibitory capacities are usually evaluated on bovine pancreatic proteases, the validity and relevance of nutritional and clinical uses of the inhibitors in other species should be questioned.
KeywordsTrypsin Inhibitor Soybean Trypsin Inhibitor Cyanogen Bromide Legume Seed Inhibitory Site
Unable to display preview. Download preview PDF.
- Friedman, M. (ed.), 1986, Nutritional and Toxicological Significance of Enzyme Inhibitors in Foods, Plenum Press, New York.Google Scholar
- Harwood, J. P., Ausman, L. M., King, N. W., Sehgal, P. K., Nicolosi, R. J., Liener, I. E., Donatucci, D., and Tarcza, J., 1985, Effect of long-term feeding of soy-based diets on the pancreas of cebus monkeys, Fed. Proc. 44:1496.Google Scholar
- Koide, T., and Ikenaka, T., 1973, Studies on soybean trypsin inhibitors. 3. Amino-acid sequence of the carboxyl-terminal region and the complete amino-acid sequence of soybean trypsin inhibitor (Kunitz), Eur. J. Biochem. 32:417–431 (as revised by Kim, S. H., Hara, S., Hase, S., Ikenaka, T., Toda, H., Kitamura, K., and Kaizuma, N., 1985, J. Biochem. 98:435-448).PubMedCrossRefGoogle Scholar
- Liener, I. E., and Kakade, M. L., 1980, Protease inhibitors, in: Toxic Constituents of Plant Foodstuffs (I. E. Liener, ed.), Academic Press, New York, pp. 7–71.Google Scholar
- Madar, Z., Birk, Y., and Gertler, A., 1974, Native and modified Bowman-Birk trypsin inhibitor— Comparative effect on pancreatic enzymes upon ingestion by quails (Coturnix coturnix japonica), Comp. Biochem. Physiol. 48B:251–256.Google Scholar
- Ryan, C. A., 1981, Proteinase inhibitors, in: The Biochemistry of Plants: A Comprehensive Treatise, Volume 6 (P. K. Stumpf and E. E. Conn, eds.), Academic Press, New York, pp. 351–371.Google Scholar
- Tamir, S., Smirnoff, P., Yonah, N., and Birk, Y., 1988, Isolation and characterization of a proteinase inhibitor from the seeds of amaranth (unpublished results).Google Scholar
- Wieczorek, M., Otlewski, J., Cook, J., Parks, K., Leluk, J., Wilimowska-Pelc, A., Polanowski, A., Wilusz, T., and Lawkowski, M., Jr., 1985, The squash family of serine proteinase inhibitors. Amino acid sequences and association equilibrium constants of inhibitors from squash, summer squash, zucchini, and cucumber seeds, Biochem. Biophys. Res. Commun. 126:646–652.PubMedCrossRefGoogle Scholar
- Yavelow, J., Finlay, T. H., Kennedy, A. R., and Troll, W., 1983, Bowman-Birk soybean protease inhibitor as an anticarcinogen, Cancer Res. 43:2454–2459.Google Scholar