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Abstract

In short-term feeding experiments, about 78% of the phaseolin administered to rats was degraded regardless of the amounts of phaseolin intubated. In contrast, the total N found in the feces increased rapidly and exceeded the original administered amounts. The bulk of N output was not immunologically related to the glycoprotein. The effects of phaseolin on the stimulation of endogenous N secretion in the small intestine were confirmed from the results of acute experiments. Phaseolin fragments, derived from the breakdown of the native protein, when reapplied intragastrically to rats, were broken down further and to a similar extent as the original glycoprotein and were even more potent related to stimulation of N secretion. It is suggested that this secretagogue biological activity of phaseolin and not its resistance to gut proteolysis, is the main reason for the poor nutritional value of this glycoprotein.

Effect of Processing on the In Vitro and In Vivo Protein Quality of Beans (Phaseolus vulgaris and Vicia Faba)

“…As the anti-nutritive factor concentration/activity would be identical between the in vitro and in vivo assessment of protein digestibility, this difference in baked flours is most likely due to confounding factors found in vivo, such as transit time through the intestine and digestive enzymes lacking access to the proteins, that are not present in the in vitro assay used in this study. It is also worth noting that phaseolin, the main storage protein in Phaseolus vulgaris , has been shown to stimulate nitrogen secretion in rats [ 38 ] and this may also act as a confounder for direct comparison between in vivo and in vitro analyses of protein digestibility.…”

Nutritional Utilization by the Rat of Diets Based on Lentil (Lens culinaris) Seed Meal or Its Fractions

“…The increased endogenous secretion might be related to abnormal local immune reactions in the intestine (). This can lead to high excretion of N in the feces, even though the globulin itself may be completely broken down before digesta moves into the large intestine ( − ).…”

Nutritional and Physiological Responses of Young Growing Rats to Diets Containing Raw Cowpea Seed Meal, Protein Isolate (Globulins), or Starch

“…The mechanisms by which legume globulins modulate gut or systemic metabolism remain unknown. However, some are mucotractive, in that they trigger excessive synthesis and secretion of mucus in the intestine ( , ). This leads to high losses of endogenous N and dry matter in the feces.…”

“…Mucin has a high carbohydrate content but a low protein content (). Thus, higher amounts of mucin present in intestinal goblet cells could slightly increase the overall weight of the intestine without greatly altering its overall protein, RNA, and DNA content ( − ). It is thus possible that the higher metabolic activity in the intestine and the increase in its proportional weight are a result of mucotractive effects of cowpea globulins on the gut.…”