A laboratory-prepared total
protein extract (TPE) and a lupin
protein isolate (LPI-E) produced in a pilot plant were submitted to a detailed two-dimensional (2DE) proteomic investigation. Recent findings have indicated that in an established rodent model of
hyperlipidemia, moderate daily intakes of LPI-Es lead to a reduction of total and
low-density lipoprotein cholesterol levels, and the knowledge of the actual composition of the
protein sample used in that study is at the basis of further structure/action investigations. The experimental results indicate that the semi-industrial procedure used for the production of LPI-E damages only marginally the
proteins. It does, however, cleave some
disulfide bridges and induce mild proteolysis, as confirmed by the higher number of resolved
protein spots in the low Mr and acidic pI region of the 2DE map. Out of 72 spots submitted to mass spectrometry and compared with available protein databases, 42 correspond to fragments of beta-conglutin, the 7S
globulin of lupin, spanning between positions 37 and 495 of the
protein sequence. Using the bioinformatic tool BlastP, these
peptides were compared to the alpha'-subunit of
beta-conglycinin, the 7S
globulin of soybean, this being the most active hypocholesterolemic component of
soybean protein, as shown by in vitro and in vivo experiments. At least 18
peptides derived from beta-conglutin, having a percentage identity higher than 50% and a similarity percentage higher than 70% vs the alpha'-subunit of
beta-conglycinin, are likely candidates to be the biologically active components of lupin
protein.