Biochemical characterization and in vitro digestibility of the major globulin in cashew nut (Anacardium occidentale)

The major globulin (anacardein) in cashew nut (Anacardium occidentale) is a 13S globulin. The globulin is not a glycoprotein and is composed of at least two major types of polypeptides with estimated molecular weights in the range 18000-24000 and 30000-37000. The globulin has A(280nm)(1%) of 9.88, 10.56, 9.68, and 9.59 in distilled water, 0.5 M NaCl, 0.02 M sodium phosphate buffer pH 7.5, and 0.02 M Tris-HCl buffer pH 8.1, respectively. The Stokes radius of the globulin was 57+/- 3.2 Angstrom (n=17). The isoelectric pH (pI) of the globulin was in the pH range 6.2-7.2. Hydrophobic, uncharged polar, acidic, and basic amino acids respectively accounted for 36.4, 19.88, 25.3, and 18.4% of the total amino acids. Sulfur amino acids and threonine were respectively the first and second limiting amino acids in the purified globulin. Among the proteinases tested, pepsin was the most efficient in hydrolyzing the globulin in vitro.