Biochemical characterization of cowpea seed proteins

Total seed proteins and the albumin and globulin fractions were analysed in 35 accessions using various electrophoretic techniques. Two major pattern types for total proteins were observed; 8 accessions possessed 23- and 32-kDa globulin subunits (type A) while the remaining 27 accessions lacked them (type B). The seed albumin fraction proved heterogeneous; the accessions differed in number, molecular weight and relative intensity of polypeptides belonging to the 63- and 95-kDa major subunits. Two major globulins, CP1 and CP2, were observed in all accessions. CP1 consisted of the 49-, 58- and 63-kDa major subunits, while CP2 was more complex, also having the 49- and 58-kDa subunits as well as the 23- and 32-kDa units of protein pattern type A accessions. The 3 major subunits were heterogeneous and consisted of similar multiple charge forms in the pH range 4.6-5.1. Three globulin subunits, with molecular weight 94,5, 87 and 40 kD, were found to be composed of disulfide-linked subunits. Since the 87 kD subunit consists oh both acidic (63 kD) and basic (22 kD) disukfide-bonded polypeptides, it could be considered a legumin-like component.