Characterization of the acidic lectins from winged bean seed (Psophocarpus tetragonolobus(L.)DC)

The amino acid composition of winged bean seed meal is similar to that of soybean but their storage globulins are quite different. Winged bean proteins are soluble to the extent of 60% at the pH of a meal-water slurry (pH 6.6), 80% at pH 11 but only 12% at pH 5. However, the proteins are soluble to the extent of 80% from pH 5 to 9 in 10% NaCl rising to 90% at pH 11. There are no satisfactory ways of recovering all the proteins from solution by simple changes in pH or ionic strength. Winged bean seed contains major proteins with sedimentation coefficients of 2 S and 6 S. Electrophoresis on cellulose acetate resolves three globulin fractions which we have named psophocarpins A, B, and C. The proteins from these electrophoretic regions have been isolated and partially purified. Psophocarpin A is essentially a single protein comparatively rich in sulfur-containing amino acids while the other fractions are composed of a number of related components which have not been separated. When examined by SDS-polyacrylamide gel electrophoresis, the globulin fractions differed in the kind of subunit proteins they contain and in the extent of disulfide bonding. The 40 000 mol. wt subunit of psophocarpin A contains disulfide bonded chains of mol. wt 16 000 and 24 000. The proteins corresponding to the other electrophoretic regions are more complex.

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Specificity and stability of the chymotrypsin inhibitor from winged bean seed (Psophocarpus tetragonolobus (L) Dc.)

Biochimica et Biophysica Acta (BBA) - Enzymology ◽

10.1016/0005-2744(81)90145-5 ◽

1981 ◽

Vol 657 (1) ◽

pp. 212-221 ◽

Cited By ~ 10

Author(s):

Alexander A. Kortt

Keyword(s):

Winged Bean ◽

Bean Seed ◽

Psophocarpus Tetragonolobus ◽

Chymotrypsin Inhibitor

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Proteases of germinating winged-bean (Psophocarpus tetragonolobus) seeds: purification and characterization of an acidic protease

Biochemical Journal ◽

10.1042/bj3130423 ◽

1996 ◽

Vol 313 (2) ◽

pp. 423-429 ◽

Cited By ~ 9

Author(s):

Rajamma USHA ◽

Manoranjan SINGH

Keyword(s):

Physiological Role ◽

Immunoblot Analysis ◽

Protein Band ◽

Winged Bean ◽

Psophocarpus Tetragonolobus ◽

Ph Optimum ◽

Apparent Homogeneity ◽

Sds Page ◽

Storage Protein Mobilization

Two major classes of protease are shown to occur in germinating winged-bean (Psophocarpus tetragonolobus) seeds, by assaying extracts at pH 8.0 and pH 5.1 with [14C]gelatin as substrate. At pH 8.0, the activity profile of the enzyme shows a steady rise throughout the period of germination, whereas the activity at the acidic pH is very low up to day 5 and then increases sharply reaching a peak on day 11, followed by an equally sharp decline. The winged-bean acidic protease (WbAP) has been purified to apparent homogeneity, as attested by a single protein band on both PAGE and SDS/PAGE. WbAP is a monomeric enzyme with a molecular mass of 35 kDa and a pH optimum of 6.0. It is a thiol protease that does not belong to the papain family and it has tightly bound Ca2+ as shown by 45Ca2+-exchange studies. Besides gelatin and casein, it hydrolyses a 29 kDa winged-bean protein, indicating a prospective physiological role for it in storage-protein mobilization. Immunoblot analysis shows that it occurs only in the seeds and sprouting tubers of this plant and also that it is synthesized in developing seeds just before desiccation. It appears that the newly synthesized enzyme is inactive, and activation takes place around day 6 of germination. However, neither the mechanism of activation nor the signal that triggers it is clearly understood.

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