soy protein is found in soy beans, though, not all beans. not all proteins absorb at the same rate:
Protein Digestibility Corrected Amino Acid Score - Wikipedia, the free encyclopedia
for example, that chart shows that we absorb 100% of soy protein but only 75% of the protein in black beans and 52% of the protein in peanuts. changes the way you read food labels.
that's just the chart on Wikipedia. you can find many other similar charts with different percentages, but the absorption rate from highest to lowest seems to be roughly constant.