COWPEA PROTEINS .2. CHARACTERIZATION OF WATER-EXTRACTABLE PROTEINS

Disc gel electrophoresis, gel filtration, and ultracentrifugation were used to characterize cowpea (Vigna unguiculata) water-extractable proteins (WEP) and water-extractable, acid-precipitated proteins (APP). After electrophoresis, the WEP showed four bands as compared to six bands in the APP. Ultracentrifuge analysis showed that the WEP contained four fractions with s20 values of 3.1, 8, 12.7, and 14.6, the 8S fraction being the predominant species. Fractions with molecular weights of 13 500, 20000, 25000, 50000, and a large-molecular-weight fraction (>600000) were separated from WEP on a Sephadex G-200 column. The 8-14.6S fractions were able to enter into association-dissociation reactions as evidenced by ultracentrifugation. Heating the WEP from 25 to 100 °C caused very little change in nitrogen solubility; however, electrophoresis indicated a breakdown into subunits and aggregation. Evidence from differential scanning colorimetry showed the possible formation of soluble aggregates during heating. © 1979, American Chemical Society. All rights reserved.