β-Conglycinin, one of the dominant storage proteins of soybean, is a trimer composed of three subunits, A, A′ and β. All subunits are N-glycosylated and A and A′ contain extension regions in addition to the core regions common to all subunits. Non-glycosylated individual subunits and deletion mutants (A c and A′ c ) lacking the extension regions of A and A′ were expressed in Escherichia coli. All recombinant proteins were purified to near homogeneity and appeared to have the correct conformation, as judged by CD, density-gradient centrifugation and gel-filtration profiles, indicating that the N-linked glycans and extension regions are not essential for the folding and the assembly into trimers of β-conglycinin. Densitygradient centrifugation, gel-filtration and differential scanning calorimetry profiles of the recombinant proteins and the native β-conglycinin indicated that the N-linked glycans and extension regions contribute to the dimension of β-conglycinin but not to the density and the thermal stability. Comparing the solubilities of the individual subunits with those of deletion mutants, only the A and A′ subunits were soluble at lower ionic strength (µ Ͻ 0.25) at around the pH value of the endoplasmic reticulum. This suggests that the extension regions play an important role in the prevention of aggregation in the endoplasmic reticulum in analogy with the N-linked glycans.

Amaranth seeds are rich in protein with a high nutritional value, but little is known about their bioactive compounds that could benefit health. The objectives of this research were to investigate the presence, characterization, and the anticarcinogenic properties of the peptide lunasin in amaranth seeds. Furthermore, to predict and identify other peptides in amaranth seed with potential biological activities. ELISA showed an average concentration of 11.1 microg lunasin equivalent/g total extracted protein in four genotypes of mature amaranth seeds. Glutelin fraction had the highest lunasin concentration (3.0 microg/g). Lunasin was also identified in albumin, prolamin and globulin amaranth protein fractions and even in popped amaranth seeds. Western blot analysis revealed a band at 18.5 kDa, and MALDI-TOF analysis showed that this peptide matched more than 60% of the soybean lunasin peptide sequence. Glutelin extracts digested with trypsin, showed the induction of apoptosis against HeLa cells. Prediction of other bioactive peptides in amaranth globulins and glutelins were mainly antihypertensive. This is the first study that reports the presence of a lunasin-like peptide and other potentially bioactive peptides in amaranth protein fractions.